FFmpeg/libavformat/mpeg.c

/*
 * MPEG1/2 mux/demux
 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include "avformat.h"

#define MAX_PAYLOAD_SIZE 4096
//#define DEBUG_SEEK

#undef NDEBUG
#include <assert.h>

typedef struct {
    uint8_t buffer[MAX_PAYLOAD_SIZE];
    int buffer_ptr;
    int nb_frames;    /* number of starting frame encountered (AC3) */
    int frame_start_offset; /* starting offset of the frame + 1 (0 if none) */
    uint8_t id;
    int max_buffer_size; /* in bytes */
    int packet_number;
    int64_t start_pts;
    int64_t start_dts;
    uint8_t lpcm_header[3];
    int lpcm_align;
} StreamInfo;

typedef struct {
    int packet_size; /* required packet size */
    int packet_number;
    int pack_header_freq;     /* frequency (in packets^-1) at which we send pack headers */
    int system_header_freq;
    int system_header_size;
    int mux_rate; /* bitrate in units of 50 bytes/s */
    /* stream info */
    int audio_bound;
    int video_bound;
    int is_mpeg2;
    int is_vcd;
    int is_svcd;
    int scr_stream_index; /* stream from which the system clock is
                             computed (VBR case) */
    int64_t last_scr; /* current system clock */

    double vcd_padding_bitrate;
    int64_t vcd_padding_bytes_written;

} MpegMuxContext;

#define PACK_START_CODE             ((unsigned int)0x000001ba)
#define SYSTEM_HEADER_START_CODE    ((unsigned int)0x000001bb)
#define SEQUENCE_END_CODE           ((unsigned int)0x000001b7)
#define PACKET_START_CODE_MASK      ((unsigned int)0xffffff00)
#define PACKET_START_CODE_PREFIX    ((unsigned int)0x00000100)
#define ISO_11172_END_CODE          ((unsigned int)0x000001b9)
  
/* mpeg2 */
#define PROGRAM_STREAM_MAP 0x1bc
#define PRIVATE_STREAM_1   0x1bd
#define PADDING_STREAM     0x1be
#define PRIVATE_STREAM_2   0x1bf


#define AUDIO_ID 0xc0
#define VIDEO_ID 0xe0
#define AC3_ID   0x80
#define DTS_ID   0x8a
#define LPCM_ID  0xa0

static const int lpcm_freq_tab[4] = { 48000, 96000, 44100, 32000 };

#ifdef CONFIG_ENCODERS
static AVOutputFormat mpeg1system_mux;
static AVOutputFormat mpeg1vcd_mux;
static AVOutputFormat mpeg2vob_mux;
static AVOutputFormat mpeg2svcd_mux;

static int put_pack_header(AVFormatContext *ctx, 
                           uint8_t *buf, int64_t timestamp)
{
    MpegMuxContext *s = ctx->priv_data;
    PutBitContext pb;
    
    init_put_bits(&pb, buf, 128);

    put_bits(&pb, 32, PACK_START_CODE);
    if (s->is_mpeg2) {
        put_bits(&pb, 2, 0x1);
    } else {
        put_bits(&pb, 4, 0x2);
    }
    put_bits(&pb, 3, (uint32_t)((timestamp >> 30) & 0x07));
    put_bits(&pb, 1, 1);
    put_bits(&pb, 15, (uint32_t)((timestamp >> 15) & 0x7fff));
    put_bits(&pb, 1, 1);
    put_bits(&pb, 15, (uint32_t)((timestamp) & 0x7fff));
    put_bits(&pb, 1, 1);
    if (s->is_mpeg2) {
        /* clock extension */
        put_bits(&pb, 9, 0);
    }
    put_bits(&pb, 1, 1);
    put_bits(&pb, 22, s->mux_rate);
    put_bits(&pb, 1, 1);
    if (s->is_mpeg2) {
        put_bits(&pb, 1, 1);
        put_bits(&pb, 5, 0x1f); /* reserved */
        put_bits(&pb, 3, 0); /* stuffing length */
    }
    flush_put_bits(&pb);
    return pbBufPtr(&pb) - pb.buf;
}

static int put_system_header(AVFormatContext *ctx, uint8_t *buf,int only_for_stream_id)
{
    MpegMuxContext *s = ctx->priv_data;
    int size, rate_bound, i, private_stream_coded, id;
    PutBitContext pb;

    init_put_bits(&pb, buf, 128);

    put_bits(&pb, 32, SYSTEM_HEADER_START_CODE);
    put_bits(&pb, 16, 0);
    put_bits(&pb, 1, 1);
    
    rate_bound = s->mux_rate; /* maximum bit rate of the multiplexed stream */
    put_bits(&pb, 22, rate_bound);
    put_bits(&pb, 1, 1); /* marker */
    if (s->is_vcd && only_for_stream_id==VIDEO_ID) {
        /* This header applies only to the video stream (see VCD standard p. IV-7)*/
        put_bits(&pb, 6, 0);
    } else
        put_bits(&pb, 6, s->audio_bound);

    if (s->is_vcd) {
        /* see VCD standard, p. IV-7*/
        put_bits(&pb, 1, 0); 
        put_bits(&pb, 1, 1);
    } else {
        put_bits(&pb, 1, 0); /* variable bitrate*/
        put_bits(&pb, 1, 0); /* non constrainted bit stream */
    }
    
    if (s->is_vcd) {
        /* see VCD standard p IV-7 */
        put_bits(&pb, 1, 1); /* audio locked */
        put_bits(&pb, 1, 1); /* video locked */
    } else {
        put_bits(&pb, 1, 0); /* audio locked */
        put_bits(&pb, 1, 0); /* video locked */
    }

    put_bits(&pb, 1, 1); /* marker */

    if (s->is_vcd && only_for_stream_id==AUDIO_ID) {
        /* This header applies only to the audio stream (see VCD standard p. IV-7)*/
        put_bits(&pb, 5, 0);
    } else
        put_bits(&pb, 5, s->video_bound);

    put_bits(&pb, 8, 0xff); /* reserved byte */
    
    /* audio stream info */
    private_stream_coded = 0;
    for(i=0;i<ctx->nb_streams;i++) {
        StreamInfo *stream = ctx->streams[i]->priv_data;
        
        /* For VCDs, only include the stream info for the stream
           that the pack which contains this system belongs to.
           (see VCD standard p. IV-7) */
        if ( !s->is_vcd || stream->id==only_for_stream_id
            || only_for_stream_id==0) {

            id = stream->id;
            if (id < 0xc0) {
                /* special case for private streams (AC3 use that) */
                if (private_stream_coded)
                    continue;
                private_stream_coded = 1;
                id = 0xbd;
            }
            put_bits(&pb, 8, id); /* stream ID */
            put_bits(&pb, 2, 3);
            if (id < 0xe0) {
                /* audio */
                put_bits(&pb, 1, 0);
                put_bits(&pb, 13, stream->max_buffer_size / 128);
            } else {
                /* video */
                put_bits(&pb, 1, 1);
                put_bits(&pb, 13, stream->max_buffer_size / 1024);
            }
        }
    }
    flush_put_bits(&pb);
    size = pbBufPtr(&pb) - pb.buf;
    /* patch packet size */
    buf[4] = (size - 6) >> 8;
    buf[5] = (size - 6) & 0xff;

    return size;
}

static int get_system_header_size(AVFormatContext *ctx)
{
    int buf_index, i, private_stream_coded;
    StreamInfo *stream;

    buf_index = 12;
    private_stream_coded = 0;
    for(i=0;i<ctx->nb_streams;i++) {
        stream = ctx->streams[i]->priv_data;
        if (stream->id < 0xc0) {
            if (private_stream_coded)
                continue;
            private_stream_coded = 1;
        }
        buf_index += 3;
    }
    return buf_index;
}

static int mpeg_mux_init(AVFormatContext *ctx)
{
    MpegMuxContext *s = ctx->priv_data;
    int bitrate, i, mpa_id, mpv_id, ac3_id, dts_id, lpcm_id, j;
    AVStream *st;
    StreamInfo *stream;
    int audio_bitrate;
    int video_bitrate;

    s->packet_number = 0;
    s->is_vcd = (ctx->oformat == &mpeg1vcd_mux);
    s->is_svcd = (ctx->oformat == &mpeg2svcd_mux);
    s->is_mpeg2 = (ctx->oformat == &mpeg2vob_mux || ctx->oformat == &mpeg2svcd_mux);
    
    if (s->is_vcd || s->is_svcd)
        s->packet_size = 2324; /* VCD/SVCD packet size */
    else
        s->packet_size = 2048;

    s->vcd_padding_bytes_written = 0;
    s->vcd_padding_bitrate=0;
        
    s->audio_bound = 0;
    s->video_bound = 0;
    mpa_id = AUDIO_ID;
    ac3_id = AC3_ID;
    dts_id = DTS_ID;
    mpv_id = VIDEO_ID;
    lpcm_id = LPCM_ID;
    s->scr_stream_index = -1;
    for(i=0;i<ctx->nb_streams;i++) {
        st = ctx->streams[i];
        stream = av_mallocz(sizeof(StreamInfo));
        if (!stream)
            goto fail;
        st->priv_data = stream;

        switch(st->codec.codec_type) {
        case CODEC_TYPE_AUDIO:
            if (st->codec.codec_id == CODEC_ID_AC3) {
                stream->id = ac3_id++;
            } else if (st->codec.codec_id == CODEC_ID_DTS) {
                stream->id = dts_id++;
            } else if (st->codec.codec_id == CODEC_ID_PCM_S16BE) {
                stream->id = lpcm_id++;
                for(j = 0; j < 4; j++) {
                    if (lpcm_freq_tab[j] == st->codec.sample_rate)
                        break;
                }
                if (j == 4)
                    goto fail;
                if (st->codec.channels > 8)
                    return -1;
                stream->lpcm_header[0] = 0x0c;
                stream->lpcm_header[1] = (st->codec.channels - 1) | (j << 4);
                stream->lpcm_header[2] = 0x80;
                stream->lpcm_align = st->codec.channels * 2;
            } else {
                stream->id = mpa_id++;
            }

            /* This value HAS to be used for VCD (see VCD standard, p. IV-7).
               Right now it is also used for everything else.*/
            stream->max_buffer_size = 4 * 1024; 
            s->audio_bound++;
            break;
        case CODEC_TYPE_VIDEO:
            /* by default, video is used for the SCR computation */
            if (s->scr_stream_index == -1)
                s->scr_stream_index = i;
            stream->id = mpv_id++;
            if (s->is_vcd)
                /* see VCD standard, p. IV-7*/
                stream->max_buffer_size = 46 * 1024; 
            else
                /* This value HAS to be used for SVCD (see SVCD standard, p. 26 V.2.3.2).
                   Right now it is also used for everything else.*/
                stream->max_buffer_size = 230 * 1024; 
            s->video_bound++;
            break;
        default:
            av_abort();
        }
    }
    /* if no SCR, use first stream (audio) */
    if (s->scr_stream_index == -1)
        s->scr_stream_index = 0;

    bitrate = 0;
    audio_bitrate = 0;
    video_bitrate = 0;
    for(i=0;i<ctx->nb_streams;i++) {
        st = ctx->streams[i];
        stream = (StreamInfo*) st->priv_data;
        
        bitrate += st->codec.bit_rate;

        if (stream->id==AUDIO_ID)
            audio_bitrate += st->codec.bit_rate;
        else if (stream->id==VIDEO_ID)
            video_bitrate += st->codec.bit_rate;
    }

    if (s->is_vcd) {
        double overhead_rate;

        /* The VCD standard mandates that the mux_rate field is 3528
           (see standard p. IV-6).
           The value is actually "wrong", i.e. if you calculate
           it using the normal formula and the 75 sectors per second transfer
           rate you get a different value because the real pack size is 2324,
           not 2352. But the standard explicitly specifies that the mux_rate
           field in the header must have this value.*/
        s->mux_rate=2352 * 75 / 50;    /* = 3528*/

        /* The VCD standard states that the muxed stream must be
           exactly 75 packs / second (the data rate of a single speed cdrom).
           Since the video bitrate (probably 1150000 bits/sec) will be below
           the theoretical maximum we have to add some padding packets
           to make up for the lower data rate.
           (cf. VCD standard p. IV-6 )*/

        /* Add the header overhead to the data rate.
           2279 data bytes per audio pack, 2294 data bytes per video pack*/
        overhead_rate = ((audio_bitrate / 8.0) / 2279) * (2324 - 2279);
        overhead_rate += ((video_bitrate / 8.0) / 2294) * (2324 - 2294);
        overhead_rate *= 8;
        
        /* Add padding so that the full bitrate is 2324*75 bytes/sec */
        s->vcd_padding_bitrate = 2324 * 75 * 8 - (bitrate + overhead_rate);

    } else {
        /* we increase slightly the bitrate to take into account the
           headers. XXX: compute it exactly */
        bitrate += 2000;
        s->mux_rate = (bitrate + (8 * 50) - 1) / (8 * 50);
    }
    
    if (s->is_vcd || s->is_mpeg2)
        /* every packet */
        s->pack_header_freq = 1;
    else
        /* every 2 seconds */
        s->pack_header_freq = 2 * bitrate / s->packet_size / 8;

    /* the above seems to make pack_header_freq zero sometimes */
    if (s->pack_header_freq == 0)
       s->pack_header_freq = 1;
    
    if (s->is_mpeg2)
        /* every 200 packets. Need to look at the spec.  */
        s->system_header_freq = s->pack_header_freq * 40;
    else if (s->is_vcd)
        /* the standard mandates that there are only two system headers
           in the whole file: one in the first packet of each stream.
           (see standard p. IV-7 and IV-8) */
        s->system_header_freq = 0x7fffffff;
    else
        s->system_header_freq = s->pack_header_freq * 5;
    
    for(i=0;i<ctx->nb_streams;i++) {
        stream = ctx->streams[i]->priv_data;
        stream->buffer_ptr = 0;
        stream->packet_number = 0;
        stream->start_pts = AV_NOPTS_VALUE;
        stream->start_dts = AV_NOPTS_VALUE;
    }
    s->system_header_size = get_system_header_size(ctx);
    s->last_scr = 0;
    return 0;
 fail:
    for(i=0;i<ctx->nb_streams;i++) {
        av_free(ctx->streams[i]->priv_data);
    }
    return -ENOMEM;
}

static inline void put_timestamp(ByteIOContext *pb, int id, int64_t timestamp)
{
    put_byte(pb, 
             (id << 4) | 
             (((timestamp >> 30) & 0x07) << 1) | 
             1);
    put_be16(pb, (uint16_t)((((timestamp >> 15) & 0x7fff) << 1) | 1));
    put_be16(pb, (uint16_t)((((timestamp) & 0x7fff) << 1) | 1));
}


/* return the number of padding bytes that should be inserted into
   the multiplexed stream.*/
static int get_vcd_padding_size(AVFormatContext *ctx, int64_t pts)
{
    MpegMuxContext *s = ctx->priv_data;
    int pad_bytes = 0;

    if (s->vcd_padding_bitrate > 0 && pts!=AV_NOPTS_VALUE)
    {
        int64_t full_pad_bytes;
        
        full_pad_bytes = (int64_t)((s->vcd_padding_bitrate * (pts / 90000.0)) / 8.0);
        pad_bytes = (int) (full_pad_bytes - s->vcd_padding_bytes_written);

        if (pad_bytes<0)
            /* might happen if we have already padded to a later timestamp. This
               can occur if another stream has already advanced further.*/
            pad_bytes=0;
    }

    return pad_bytes;
}


/* return the exact available payload size for the next packet for
   stream 'stream_index'. 'pts' and 'dts' are only used to know if
   timestamps are needed in the packet header. */
static int get_packet_payload_size(AVFormatContext *ctx, int stream_index,
                                   int64_t pts, int64_t dts)
{
    MpegMuxContext *s = ctx->priv_data;
    int buf_index;
    StreamInfo *stream;

    stream = ctx->streams[stream_index]->priv_data;

    buf_index = 0;
    if (((s->packet_number % s->pack_header_freq) == 0)) {
        /* pack header size */
        if (s->is_mpeg2) 
            buf_index += 14;
        else
            buf_index += 12;
        
        if (s->is_vcd) {
            /* there is exactly one system header for each stream in a VCD MPEG,
               One in the very first video packet and one in the very first
               audio packet (see VCD standard p. IV-7 and IV-8).*/
            
            if (stream->packet_number==0)
                /* The system headers refer only to the stream they occur in,
                   so they have a constant size.*/
                buf_index += 15;

        } else {            
            if ((s->packet_number % s->system_header_freq) == 0)
                buf_index += s->system_header_size;
        }
    }

    if ((s->is_vcd && stream->packet_number==0)
        || (s->is_svcd && s->packet_number==0))
        /* the first pack of each stream contains only the pack header,
           the system header and some padding (see VCD standard p. IV-6) 
           Add the padding size, so that the actual payload becomes 0.*/
        buf_index += s->packet_size - buf_index;
    else {
        /* packet header size */
        buf_index += 6;
        if (s->is_mpeg2) {
            buf_index += 3;
            if (stream->packet_number==0)
                buf_index += 3; /* PES extension */
            buf_index += 1;    /* obligatory stuffing byte */
        }
        if (pts != AV_NOPTS_VALUE) {
            if (dts != pts)
                buf_index += 5 + 5;
            else
                buf_index += 5;

        } else {
            if (!s->is_mpeg2)
                buf_index++;
        }
    
        if (stream->id < 0xc0) {
            /* AC3/LPCM private data header */
            buf_index += 4;
            if (stream->id >= 0xa0) {
                int n;
                buf_index += 3;
                /* NOTE: we round the payload size to an integer number of
                   LPCM samples */
                n = (s->packet_size - buf_index) % stream->lpcm_align;
                if (n)
                    buf_index += (stream->lpcm_align - n);
            }
        }

        if (s->is_vcd && stream->id == AUDIO_ID)
            /* The VCD standard demands that 20 zero bytes follow
               each audio packet (see standard p. IV-8).*/
            buf_index+=20;
    }
    return s->packet_size - buf_index; 
}

/* Write an MPEG padding packet header. */
static int put_padding_header(AVFormatContext *ctx,uint8_t* buf, int full_padding_size)
{
    MpegMuxContext *s = ctx->priv_data;
    int size = full_padding_size - 6;    /* subtract header length */

    buf[0] = (uint8_t)(PADDING_STREAM >> 24);
    buf[1] = (uint8_t)(PADDING_STREAM >> 16);
    buf[2] = (uint8_t)(PADDING_STREAM >> 8);
    buf[3] = (uint8_t)(PADDING_STREAM);
    buf[4] = (uint8_t)(size >> 8);
    buf[5] = (uint8_t)(size & 0xff);

    if (!s->is_mpeg2) {
        buf[6] = 0x0f;
        return 7;
    } else
        return 6;
}

static void put_padding_packet(AVFormatContext *ctx, ByteIOContext *pb,int packet_bytes)
{
    uint8_t buffer[7];
    int size, i;
    
    size = put_padding_header(ctx,buffer, packet_bytes);
    put_buffer(pb, buffer, size);
    packet_bytes -= size;

    for(i=0;i<packet_bytes;i++)
        put_byte(pb, 0xff);
}


/* flush the packet on stream stream_index */
static void flush_packet(AVFormatContext *ctx, int stream_index, 
                         int64_t pts, int64_t dts, int64_t scr)
{
    MpegMuxContext *s = ctx->priv_data;
    StreamInfo *stream = ctx->streams[stream_index]->priv_data;
    uint8_t *buf_ptr;
    int size, payload_size, startcode, id, stuffing_size, i, header_len;
    int packet_size;
    uint8_t buffer[128];
    int zero_trail_bytes = 0;
    int pad_packet_bytes = 0;
    int pes_flags;
    int general_pack = 0;  /*"general" pack without data specific to one stream?*/
    
    id = stream->id;
    
#if 0
    printf("packet ID=%2x PTS=%0.3f\n", 
           id, pts / 90000.0);
#endif

    buf_ptr = buffer;

    if (((s->packet_number % s->pack_header_freq) == 0)) {
        /* output pack and systems header if needed */
        size = put_pack_header(ctx, buf_ptr, scr);
        buf_ptr += size;

        if (s->is_vcd) {
            /* there is exactly one system header for each stream in a VCD MPEG,
               One in the very first video packet and one in the very first
               audio packet (see VCD standard p. IV-7 and IV-8).*/
            
            if (stream->packet_number==0) {
                size = put_system_header(ctx, buf_ptr, id);
                buf_ptr += size;
            }
        } else {
            if ((s->packet_number % s->system_header_freq) == 0) {
                size = put_system_header(ctx, buf_ptr, 0);
                buf_ptr += size;
            }
        }
    }
    size = buf_ptr - buffer;
    put_buffer(&ctx->pb, buffer, size);

    packet_size = s->packet_size - size;

    if (s->is_vcd && id == AUDIO_ID)
        /* The VCD standard demands that 20 zero bytes follow
           each audio pack (see standard p. IV-8).*/
        zero_trail_bytes += 20;
            
    if ((s->is_vcd && stream->packet_number==0)
        || (s->is_svcd && s->packet_number==0)) {
        /* for VCD the first pack of each stream contains only the pack header,
           the system header and lots of padding (see VCD standard p. IV-6).
           In the case of an audio pack, 20 zero bytes are also added at
           the end.*/
        /* For SVCD we fill the very first pack to increase compatibility with
           some DVD players. Not mandated by the standard.*/
        if (s->is_svcd)
            general_pack = 1;    /* the system header refers to both streams and no stream data*/
        pad_packet_bytes = packet_size - zero_trail_bytes;
    }

    packet_size -= pad_packet_bytes + zero_trail_bytes;

    if (packet_size > 0) {

        /* packet header size */
        packet_size -= 6;
        
        /* packet header */
        if (s->is_mpeg2) {
            header_len = 3;
            if (stream->packet_number==0)
                header_len += 3; /* PES extension */
            header_len += 1; /* obligatory stuffing byte */
        } else {
            header_len = 0;
        }
        if (pts != AV_NOPTS_VALUE) {
            if (dts != pts)
                header_len += 5 + 5;
            else
                header_len += 5;
        } else {
            if (!s->is_mpeg2)
                header_len++;
        }

        payload_size = packet_size - header_len;
        if (id < 0xc0) {
            startcode = PRIVATE_STREAM_1;
            payload_size -= 4;
            if (id >= 0xa0)
                payload_size -= 3;
        } else {
            startcode = 0x100 + id;
        }

        stuffing_size = payload_size - stream->buffer_ptr;
        if (stuffing_size < 0)
            stuffing_size = 0;
        if (stuffing_size > 16) {    /*<=16 for MPEG-1, <=32 for MPEG-2*/
            pad_packet_bytes += stuffing_size;
            packet_size -= stuffing_size;
            payload_size -= stuffing_size;
            stuffing_size = 0;
        }

        put_be32(&ctx->pb, startcode);

        put_be16(&ctx->pb, packet_size);
        
        if (!s->is_mpeg2)
            for(i=0;i<stuffing_size;i++)
                put_byte(&ctx->pb, 0xff);

        if (s->is_mpeg2) {
            put_byte(&ctx->pb, 0x80); /* mpeg2 id */

            pes_flags=0;

            if (pts != AV_NOPTS_VALUE) {
                pes_flags |= 0x80;
                if (dts != pts)
                    pes_flags |= 0x40;
            }

            /* Both the MPEG-2 and the SVCD standards demand that the
               P-STD_buffer_size field be included in the first packet of
               every stream. (see SVCD standard p. 26 V.2.3.1 and V.2.3.2
               and MPEG-2 standard 2.7.7) */
            if (stream->packet_number == 0)
                pes_flags |= 0x01;

            put_byte(&ctx->pb, pes_flags); /* flags */
            put_byte(&ctx->pb, header_len - 3 + stuffing_size);

            if (pes_flags & 0x80)  /*write pts*/
                put_timestamp(&ctx->pb, (pes_flags & 0x40) ? 0x03 : 0x02, pts);
            if (pes_flags & 0x40)  /*write dts*/
                put_timestamp(&ctx->pb, 0x01, dts);
            
            if (pes_flags & 0x01) {  /*write pes extension*/
                put_byte(&ctx->pb, 0x10); /* flags */

                /* P-STD buffer info */                
                if (id == AUDIO_ID)
                    put_be16(&ctx->pb, 0x4000 | stream->max_buffer_size/128);
                else
                    put_be16(&ctx->pb, 0x6000 | stream->max_buffer_size/1024);
            }

        } else {
            if (pts != AV_NOPTS_VALUE) {
                if (dts != pts) {
                    put_timestamp(&ctx->pb, 0x03, pts);
                    put_timestamp(&ctx->pb, 0x01, dts);
                } else {
                    put_timestamp(&ctx->pb, 0x02, pts);
                }
            } else {
                put_byte(&ctx->pb, 0x0f);
            }
        }

        if (s->is_mpeg2) {
            /* special stuffing byte that is always written
               to prevent accidental generation of start codes. */
            put_byte(&ctx->pb, 0xff);

            for(i=0;i<stuffing_size;i++)
                put_byte(&ctx->pb, 0xff);
        }

        if (startcode == PRIVATE_STREAM_1) {
            put_byte(&ctx->pb, id);
            if (id >= 0xa0) {
                /* LPCM (XXX: check nb_frames) */
                put_byte(&ctx->pb, 7);
                put_be16(&ctx->pb, 4); /* skip 3 header bytes */
                put_byte(&ctx->pb, stream->lpcm_header[0]);
                put_byte(&ctx->pb, stream->lpcm_header[1]);
                put_byte(&ctx->pb, stream->lpcm_header[2]);
            } else {
                /* AC3 */
                put_byte(&ctx->pb, stream->nb_frames);
                put_be16(&ctx->pb, stream->frame_start_offset);
            }
        }

        /* output data */
        put_buffer(&ctx->pb, stream->buffer, payload_size - stuffing_size);
    }

    if (pad_packet_bytes > 0)
        put_padding_packet(ctx,&ctx->pb, pad_packet_bytes);    

    for(i=0;i<zero_trail_bytes;i++)
        put_byte(&ctx->pb, 0x00);
        
    put_flush_packet(&ctx->pb);
    
    s->packet_number++;

    /* only increase the stream packet number if this pack actually contains
       something that is specific to this stream! I.e. a dedicated header
       or some data.*/
    if (!general_pack)
        stream->packet_number++;
    stream->nb_frames = 0;
    stream->frame_start_offset = 0;
}

static void put_vcd_padding_sector(AVFormatContext *ctx)
{
    /* There are two ways to do this padding: writing a sector/pack
       of 0 values, or writing an MPEG padding pack. Both seem to
       work with most decoders, BUT the VCD standard only allows a 0-sector
       (see standard p. IV-4, IV-5).
       So a 0-sector it is...*/

    MpegMuxContext *s = ctx->priv_data;
    int i;

    for(i=0;i<s->packet_size;i++)
        put_byte(&ctx->pb, 0);

    s->vcd_padding_bytes_written += s->packet_size;
        
    put_flush_packet(&ctx->pb);
    
    /* increasing the packet number is correct. The SCR of the following packs
       is calculated from the packet_number and it has to include the padding
       sector (it represents the sector index, not the MPEG pack index)
       (see VCD standard p. IV-6)*/
    s->packet_number++;
}

static int64_t update_scr(AVFormatContext *ctx,int stream_index,int64_t pts)
{
    MpegMuxContext *s = ctx->priv_data;
    int64_t scr;
    StreamInfo *stream;
    int i;

    if (s->is_vcd) {
        /* Since the data delivery rate is constant, SCR is computed
           using the formula C + i * 1200 where C is the start constant
           and i is the pack index.
           It is recommended that SCR 0 is at the beginning of the VCD front
           margin (a sequence of empty Form 2 sectors on the CD).
           It is recommended that the front margin is 30 sectors long, so
           we use C = 30*1200 = 36000
           (Note that even if the front margin is not 30 sectors the file
           will still be correct according to the standard. It just won't have
           the "recommended" value).*/
        scr = 36000 + s->packet_number * 1200;


#if 0
        for(i=0;i<ctx->nb_streams;i++) {
            stream = ctx->streams[i]->priv_data;
            
            if(scr > stream->start_pts && stream->start_pts!=AV_NOPTS_VALUE) {
                av_log(ctx, AV_LOG_DEBUG, "mpeg vcd: SCR above PTS (scr=%0.3f, stream index=%d, stream_pts=%0.3f).\n", scr/90000.0, i, stream->start_pts / 90000.0);                 
            }
        }
#endif
    }
    else {
        
        
        /* XXX I believe this calculation of SCR is wrong. SCR
           specifies at which time the data should enter the decoder.
           Two packs cannot enter the decoder at the same time. */

        /* XXX: system clock should be computed precisely, especially for
        CBR case. The current mode gives at least something coherent */
        if (stream_index == s->scr_stream_index
            && pts != AV_NOPTS_VALUE)
            scr = pts;
        else
            scr = s->last_scr;

        /* "Sanity hack": make sure that the SCR does not overtake the pts of
           buffered data that is still waiting to be written.*/
        for(i=0;i<ctx->nb_streams;i++) {
            stream = ctx->streams[i]->priv_data;
            
            if(scr > stream->start_pts && stream->start_pts!=AV_NOPTS_VALUE) {
                /* av_log(ctx, AV_LOG_DEBUG, "mpeg: restricting scr to stream pts (scr=%0.3f, stream index=%d, stream_pts=%0.3f).\n", scr/90000.0, i, stream->start_pts / 90000.0); */
                scr = stream->start_pts;
            }
        }
    }

    s->last_scr=scr;

    return scr;
}    


static int mpeg_mux_write_packet(AVFormatContext *ctx, AVPacket *pkt)
{
    MpegMuxContext *s = ctx->priv_data;
    int stream_index= pkt->stream_index;
    int size= pkt->size;
    uint8_t *buf= pkt->data;
    AVStream *st = ctx->streams[stream_index];
    StreamInfo *stream = st->priv_data;
    int64_t pts, dts, new_start_pts, new_start_dts;
    int len, avail_size;
    
    pts= pkt->pts;
    dts= pkt->dts;

    if(s->is_svcd) {
        /* offset pts and dts slightly into the future to be able
           to do the compatibility fix below.*/
        pts = (pts + 2) & ((1LL << 33) - 1);
        dts = (dts + 2) & ((1LL << 33) - 1);

        if (stream->packet_number == 0 && dts == pts)
            /* For the very first packet we want to force the DTS to be included.
               This increases compatibility with lots of DVD players.
               Since the MPEG-2 standard mandates that DTS is only written when
               it is different from PTS we have to move it slightly into the past.*/
            dts = (dts - 2) & ((1LL << 33) - 1);
    }
    if(s->is_vcd) {
        /* We have to offset the PTS, so that it is consistent with the SCR.
           SCR starts at 36000, but the first two packs contain only padding
           and the first pack from the other stream, respectively, may also have
           been written before.
           So the real data starts at SCR 36000+3*1200. */
        pts = (pts + 36000 + 3600) & ((1LL << 33) - 1);
        dts = (dts + 36000 + 3600) & ((1LL << 33) - 1);
    }
    
#if 0
    update_scr(ctx,stream_index,pts);

    printf("%d: pts=%0.3f dts=%0.3f scr=%0.3f\n", 
           stream_index, 
           pts / 90000.0, 
           dts / 90000.0, 
           s->last_scr / 90000.0);
#endif
    
    /* we assume here that pts != AV_NOPTS_VALUE */
    new_start_pts = stream->start_pts;
    new_start_dts = stream->start_dts;
    
    if (stream->start_pts == AV_NOPTS_VALUE) {
        new_start_pts = pts;
        new_start_dts = dts;
    }
    avail_size = get_packet_payload_size(ctx, stream_index,
                                         new_start_pts, 
                                         new_start_dts);
    if (stream->buffer_ptr >= avail_size) {

        update_scr(ctx,stream_index,stream->start_pts);

        /* unlikely case: outputing the pts or dts increase the packet
           size so that we cannot write the start of the next
           packet. In this case, we must flush the current packet with
           padding.
           Note: this always happens for the first audio and video packet
           in a VCD file, since they do not carry any data.*/
        flush_packet(ctx, stream_index,
                     stream->start_pts, stream->start_dts, s->last_scr);
        stream->buffer_ptr = 0;
    }
    stream->start_pts = new_start_pts;
    stream->start_dts = new_start_dts;
    stream->nb_frames++;
    if (stream->frame_start_offset == 0)
        stream->frame_start_offset = stream->buffer_ptr + 1;
    while (size > 0) {
        avail_size = get_packet_payload_size(ctx, stream_index,
                                             stream->start_pts, 
                                             stream->start_dts);
        len = avail_size - stream->buffer_ptr;
        if (len > size)
            len = size;
        memcpy(stream->buffer + stream->buffer_ptr, buf, len);
        stream->buffer_ptr += len;
        buf += len;
        size -= len;
        if (stream->buffer_ptr >= avail_size) {

            update_scr(ctx,stream_index,stream->start_pts);

            /* if packet full, we send it now */
            flush_packet(ctx, stream_index,
                         stream->start_pts, stream->start_dts, s->last_scr);
            stream->buffer_ptr = 0;

            if (s->is_vcd) {
                /* Write one or more padding sectors, if necessary, to reach
                   the constant overall bitrate.*/
                int vcd_pad_bytes;
            
                while((vcd_pad_bytes = get_vcd_padding_size(ctx,stream->start_pts) ) >= s->packet_size)
                    put_vcd_padding_sector(ctx);
            }

            /* Make sure only the FIRST pes packet for this frame has
               a timestamp */
            stream->start_pts = AV_NOPTS_VALUE;
            stream->start_dts = AV_NOPTS_VALUE;
        }
    }

    return 0;
}

static int mpeg_mux_end(AVFormatContext *ctx)
{
    MpegMuxContext *s = ctx->priv_data;
    StreamInfo *stream;
    int i;

    /* flush each packet */
    for(i=0;i<ctx->nb_streams;i++) {
        stream = ctx->streams[i]->priv_data;
        if (stream->buffer_ptr > 0) {
            update_scr(ctx,i,stream->start_pts);

            /* NOTE: we can always write the remaining data as it was
               tested before in mpeg_mux_write_packet() */
            flush_packet(ctx, i, stream->start_pts, stream->start_dts, 
                         s->last_scr);
        }
    }

    /* End header according to MPEG1 systems standard. We do not write
       it as it is usually not needed by decoders and because it
       complicates MPEG stream concatenation. */
    //put_be32(&ctx->pb, ISO_11172_END_CODE);
    //put_flush_packet(&ctx->pb);

    for(i=0;i<ctx->nb_streams;i++)
        av_freep(&ctx->streams[i]->priv_data);

    return 0;
}
#endif //CONFIG_ENCODERS

/*********************************************/
/* demux code */

#define MAX_SYNC_SIZE 100000

static int mpegps_probe(AVProbeData *p)
{
    int code, c, i;

    code = 0xff;
    /* we search the first start code. If it is a packet start code,
       then we decide it is mpeg ps. We do not send highest value to
       give a chance to mpegts */
    /* NOTE: the search range was restricted to avoid too many false
       detections */

    if (p->buf_size < 6)
        return 0;

    for (i = 0; i < 20; i++) {
        c = p->buf[i];
        code = (code << 8) | c;
        if ((code & 0xffffff00) == 0x100) {
            if (code == PACK_START_CODE ||
                code == SYSTEM_HEADER_START_CODE ||
                (code >= 0x1e0 && code <= 0x1ef) ||
                (code >= 0x1c0 && code <= 0x1df) ||
                code == PRIVATE_STREAM_2 ||
                code == PROGRAM_STREAM_MAP ||
                code == PRIVATE_STREAM_1 ||
                code == PADDING_STREAM)
                return AVPROBE_SCORE_MAX - 2;
            else
                return 0;
        }
    }
    return 0;
}


typedef struct MpegDemuxContext {
    int header_state;
} MpegDemuxContext;

static int mpegps_read_header(AVFormatContext *s,
                              AVFormatParameters *ap)
{
    MpegDemuxContext *m = s->priv_data;
    m->header_state = 0xff;
    s->ctx_flags |= AVFMTCTX_NOHEADER;

    /* no need to do more */
    return 0;
}

static int64_t get_pts(ByteIOContext *pb, int c)
{
    int64_t pts;
    int val;

    if (c < 0)
        c = get_byte(pb);
    pts = (int64_t)((c >> 1) & 0x07) << 30;
    val = get_be16(pb);
    pts |= (int64_t)(val >> 1) << 15;
    val = get_be16(pb);
    pts |= (int64_t)(val >> 1);
    return pts;
}

static int find_next_start_code(ByteIOContext *pb, int *size_ptr, 
                                uint32_t *header_state)
{
    unsigned int state, v;
    int val, n;

    state = *header_state;
    n = *size_ptr;
    while (n > 0) {
        if (url_feof(pb))
            break;
        v = get_byte(pb);
        n--;
        if (state == 0x000001) {
            state = ((state << 8) | v) & 0xffffff;
            val = state;
            goto found;
        }
        state = ((state << 8) | v) & 0xffffff;
    }
    val = -1;
 found:
    *header_state = state;
    *size_ptr = n;
    return val;
}

/* XXX: optimize */
static int find_prev_start_code(ByteIOContext *pb, int *size_ptr)
{
    int64_t pos, pos_start;
    int max_size, start_code;

    max_size = *size_ptr;
    pos_start = url_ftell(pb);

    /* in order to go faster, we fill the buffer */
    pos = pos_start - 16386;
    if (pos < 0)
        pos = 0;
    url_fseek(pb, pos, SEEK_SET);
    get_byte(pb);

    pos = pos_start;
    for(;;) {
        pos--;
        if (pos < 0 || (pos_start - pos) >= max_size) {
            start_code = -1;
            goto the_end;
        }
        url_fseek(pb, pos, SEEK_SET);
        start_code = get_be32(pb);
        if ((start_code & 0xffffff00) == 0x100)
            break;
    }
 the_end:
    *size_ptr = pos_start - pos;
    return start_code;
}

/* read the next PES header. Return its position in ppos 
   (if not NULL), and its start code, pts and dts.
 */
static int mpegps_read_pes_header(AVFormatContext *s,
                                  int64_t *ppos, int *pstart_code, 
                                  int64_t *ppts, int64_t *pdts)
{
    MpegDemuxContext *m = s->priv_data;
    int len, size, startcode, c, flags, header_len;
    int64_t pts, dts, last_pos;

    last_pos = -1;
 redo:
        /* next start code (should be immediately after) */
        m->header_state = 0xff;
        size = MAX_SYNC_SIZE;
        startcode = find_next_start_code(&s->pb, &size, &m->header_state);
    //printf("startcode=%x pos=0x%Lx\n", startcode, url_ftell(&s->pb));
    if (startcode < 0)
        return AVERROR_IO;
    if (startcode == PACK_START_CODE)
        goto redo;
    if (startcode == SYSTEM_HEADER_START_CODE)
        goto redo;
    if (startcode == PADDING_STREAM ||
        startcode == PRIVATE_STREAM_2) {
        /* skip them */
        len = get_be16(&s->pb);
        url_fskip(&s->pb, len);
        goto redo;
    }
    /* find matching stream */
    if (!((startcode >= 0x1c0 && startcode <= 0x1df) ||
          (startcode >= 0x1e0 && startcode <= 0x1ef) ||
          (startcode == 0x1bd)))
        goto redo;
    if (ppos) {
        *ppos = url_ftell(&s->pb) - 4;
    }
    len = get_be16(&s->pb);
    pts = AV_NOPTS_VALUE;
    dts = AV_NOPTS_VALUE;
    /* stuffing */
    for(;;) {
        if (len < 1)
            goto redo;
        c = get_byte(&s->pb);
        len--;
        /* XXX: for mpeg1, should test only bit 7 */
        if (c != 0xff) 
            break;
    }
    if ((c & 0xc0) == 0x40) {
        /* buffer scale & size */
        if (len < 2)
            goto redo;
        get_byte(&s->pb);
        c = get_byte(&s->pb);
        len -= 2;
    }
    if ((c & 0xf0) == 0x20) {
        if (len < 4)
            goto redo;
        dts = pts = get_pts(&s->pb, c);
        len -= 4;
    } else if ((c & 0xf0) == 0x30) {
        if (len < 9)
            goto redo;
        pts = get_pts(&s->pb, c);
        dts = get_pts(&s->pb, -1);
        len -= 9;
    } else if ((c & 0xc0) == 0x80) {
        /* mpeg 2 PES */
        if ((c & 0x30) != 0) {
            /* Encrypted multiplex not handled */
            goto redo;
        }
        flags = get_byte(&s->pb);
        header_len = get_byte(&s->pb);
        len -= 2;
        if (header_len > len)
            goto redo;
        if ((flags & 0xc0) == 0x80) {
            dts = pts = get_pts(&s->pb, -1);
            if (header_len < 5)
                goto redo;
            header_len -= 5;
            len -= 5;
        } if ((flags & 0xc0) == 0xc0) {
            pts = get_pts(&s->pb, -1);
            dts = get_pts(&s->pb, -1);
            if (header_len < 10)
                goto redo;
            header_len -= 10;
            len -= 10;
        }
        len -= header_len;
        while (header_len > 0) {
            get_byte(&s->pb);
            header_len--;
        }
    }
    else if( c!= 0xf )
        goto redo;

    if (startcode == 0x1bd) {
        if (len < 1)
            goto redo;
        startcode = get_byte(&s->pb);
        len--;
        if (startcode >= 0x80 && startcode <= 0xbf) {
            /* audio: skip header */
            if (len < 3)
                goto redo;
            get_byte(&s->pb);
            get_byte(&s->pb);
            get_byte(&s->pb);
            len -= 3;
        }
    }
    if(dts != AV_NOPTS_VALUE && ppos){
        int i;
        for(i=0; i<s->nb_streams; i++){
            if(startcode == s->streams[i]->id) {
                av_add_index_entry(s->streams[i], *ppos, dts, 0, 0 /* FIXME keyframe? */);
            }
        }
    }
    
    *pstart_code = startcode;
    *ppts = pts;
    *pdts = dts;
    return len;
}

static int mpegps_read_packet(AVFormatContext *s,
                              AVPacket *pkt)
{
    AVStream *st;
    int len, startcode, i, type, codec_id = 0;
    int64_t pts, dts, dummy_pos; //dummy_pos is needed for the index building to work

 redo:
    len = mpegps_read_pes_header(s, &dummy_pos, &startcode, &pts, &dts);
    if (len < 0)
        return len;
    
    /* now find stream */
    for(i=0;i<s->nb_streams;i++) {
        st = s->streams[i];
        if (st->id == startcode)
            goto found;
    }
    if (startcode >= 0x1e0 && startcode <= 0x1ef) {
        type = CODEC_TYPE_VIDEO;
        codec_id = CODEC_ID_MPEG2VIDEO;
    } else if (startcode >= 0x1c0 && startcode <= 0x1df) {
        type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_MP2;
    } else if (startcode >= 0x80 && startcode <= 0x89) {
        type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_AC3;
    } else if (startcode >= 0x8a && startcode <= 0x9f) {
        type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_DTS;
    } else if (startcode >= 0xa0 && startcode <= 0xbf) {
        type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_PCM_S16BE;
    } else {
    skip:
        /* skip packet */
        url_fskip(&s->pb, len);
        goto redo;
    }
    /* no stream found: add a new stream */
    st = av_new_stream(s, startcode);
    if (!st) 
        goto skip;
    st->codec.codec_type = type;
    st->codec.codec_id = codec_id;
    if (codec_id != CODEC_ID_PCM_S16BE)
        st->need_parsing = 1;
 found:
    if (startcode >= 0xa0 && startcode <= 0xbf) {
        int b1, freq;

        /* for LPCM, we just skip the header and consider it is raw
           audio data */
        if (len <= 3)
            goto skip;
        get_byte(&s->pb); /* emphasis (1), muse(1), reserved(1), frame number(5) */
        b1 = get_byte(&s->pb); /* quant (2), freq(2), reserved(1), channels(3) */
        get_byte(&s->pb); /* dynamic range control (0x80 = off) */
        len -= 3;
        freq = (b1 >> 4) & 3;
        st->codec.sample_rate = lpcm_freq_tab[freq];
        st->codec.channels = 1 + (b1 & 7);
        st->codec.bit_rate = st->codec.channels * st->codec.sample_rate * 2;
    }
    av_new_packet(pkt, len);
    get_buffer(&s->pb, pkt->data, pkt->size);
    pkt->pts = pts;
    pkt->dts = dts;
    pkt->stream_index = st->index;
#if 0
    av_log(s, AV_LOG_DEBUG, "%d: pts=%0.3f dts=%0.3f\n",
           pkt->stream_index, pkt->pts / 90000.0, pkt->dts / 90000.0);
#endif

    return 0;
}

static int mpegps_read_close(AVFormatContext *s)
{
    return 0;
}

static int64_t mpegps_read_dts(AVFormatContext *s, int stream_index, 
                               int64_t *ppos, int64_t pos_limit)
{
    int len, startcode;
    int64_t pos, pts, dts;

    pos = *ppos;
#ifdef DEBUG_SEEK
    printf("read_dts: pos=0x%llx next=%d -> ", pos, find_next);
#endif
    url_fseek(&s->pb, pos, SEEK_SET);
    for(;;) {
        len = mpegps_read_pes_header(s, &pos, &startcode, &pts, &dts);
        if (len < 0) {
#ifdef DEBUG_SEEK
            printf("none (ret=%d)\n", len);
#endif
            return AV_NOPTS_VALUE;
        }
        if (startcode == s->streams[stream_index]->id && 
            dts != AV_NOPTS_VALUE) {
            break;
        }
        url_fskip(&s->pb, len);
    }
#ifdef DEBUG_SEEK
    printf("pos=0x%llx dts=0x%llx %0.3f\n", pos, dts, dts / 90000.0);
#endif
    *ppos = pos;
    return dts;
}

#ifdef CONFIG_ENCODERS
static AVOutputFormat mpeg1system_mux = {
    "mpeg",
    "MPEG1 System format",
    "video/mpeg",
    "mpg,mpeg",
    sizeof(MpegMuxContext),
    CODEC_ID_MP2,
    CODEC_ID_MPEG1VIDEO,
    mpeg_mux_init,
    mpeg_mux_write_packet,
    mpeg_mux_end,
};

static AVOutputFormat mpeg1vcd_mux = {
    "vcd",
    "MPEG1 System format (VCD)",
    "video/mpeg",
    NULL,
    sizeof(MpegMuxContext),
    CODEC_ID_MP2,
    CODEC_ID_MPEG1VIDEO,
    mpeg_mux_init,
    mpeg_mux_write_packet,
    mpeg_mux_end,
};

static AVOutputFormat mpeg2vob_mux = {
    "vob",
    "MPEG2 PS format (VOB)",
    "video/mpeg",
    "vob",
    sizeof(MpegMuxContext),
    CODEC_ID_MP2,
    CODEC_ID_MPEG2VIDEO,
    mpeg_mux_init,
    mpeg_mux_write_packet,
    mpeg_mux_end,
};

/* Same as mpeg2vob_mux except that the pack size is 2324 */
static AVOutputFormat mpeg2svcd_mux = {
    "svcd",
    "MPEG2 PS format (VOB)",
    "video/mpeg",
    "vob",
    sizeof(MpegMuxContext),
    CODEC_ID_MP2,
    CODEC_ID_MPEG2VIDEO,
    mpeg_mux_init,
    mpeg_mux_write_packet,
    mpeg_mux_end,
};



#endif //CONFIG_ENCODERS

AVInputFormat mpegps_demux = {
    "mpeg",
    "MPEG PS format",
    sizeof(MpegDemuxContext),
    mpegps_probe,
    mpegps_read_header,
    mpegps_read_packet,
    mpegps_read_close,
    NULL, //mpegps_read_seek,
    mpegps_read_dts,
};

int mpegps_init(void)
{
#ifdef CONFIG_ENCODERS
    av_register_output_format(&mpeg1system_mux);
    av_register_output_format(&mpeg1vcd_mux);
    av_register_output_format(&mpeg2vob_mux);
    av_register_output_format(&mpeg2svcd_mux);
#endif //CONFIG_ENCODERS
    av_register_input_format(&mpegps_demux);
    return 0;
}