FFmpeg/libavformat/format.c

/*
 * Format register and lookup
 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
 *
 * This file is part of Libav.
 *
 * Libav 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 2.1 of the License, or (at your option) any later version.
 *
 * Libav 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 Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/avstring.h"

#include "avio_internal.h"
#include "avformat.h"
#include "id3v2.h"
#include "internal.h"

/**
 * @file
 * Format register and lookup
 */
/** head of registered input format linked list */
static AVInputFormat *first_iformat = NULL;
/** head of registered output format linked list */
static AVOutputFormat *first_oformat = NULL;

AVInputFormat *av_iformat_next(const AVInputFormat *f)
{
    if (f)
        return f->next;
    else
        return first_iformat;
}

AVOutputFormat *av_oformat_next(const AVOutputFormat *f)
{
    if (f)
        return f->next;
    else
        return first_oformat;
}

void av_register_input_format(AVInputFormat *format)
{
    AVInputFormat **p = &first_iformat;

    while (*p != NULL)
        p = &(*p)->next;

    *p = format;
    format->next = NULL;
}

void av_register_output_format(AVOutputFormat *format)
{
    AVOutputFormat **p = &first_oformat;

    while (*p != NULL)
        p = &(*p)->next;

    *p = format;
    format->next = NULL;
}

int av_match_ext(const char *filename, const char *extensions)
{
    const char *ext, *p;
    char ext1[32], *q;

    if (!filename)
        return 0;

    ext = strrchr(filename, '.');
    if (ext) {
        ext++;
        p = extensions;
        for (;;) {
            q = ext1;
            while (*p != '\0' && *p != ','  && q - ext1 < sizeof(ext1) - 1)
                *q++ = *p++;
            *q = '\0';
            if (!av_strcasecmp(ext1, ext))
                return 1;
            if (*p == '\0')
                break;
            p++;
        }
    }
    return 0;
}

static int match_format(const char *name, const char *names)
{
    const char *p;
    int len, namelen;

    if (!name || !names)
        return 0;

    namelen = strlen(name);
    while ((p = strchr(names, ','))) {
        len = FFMAX(p - names, namelen);
        if (!av_strncasecmp(name, names, len))
            return 1;
        names = p + 1;
    }
    return !av_strcasecmp(name, names);
}

AVOutputFormat *av_guess_format(const char *short_name, const char *filename,
                                const char *mime_type)
{
    AVOutputFormat *fmt = NULL, *fmt_found;
    int score_max, score;

    /* specific test for image sequences */
#if CONFIG_IMAGE2_MUXER
    if (!short_name && filename &&
        av_filename_number_test(filename) &&
        ff_guess_image2_codec(filename) != AV_CODEC_ID_NONE) {
        return av_guess_format("image2", NULL, NULL);
    }
#endif
    /* Find the proper file type. */
    fmt_found = NULL;
    score_max = 0;
    while ((fmt = av_oformat_next(fmt))) {
        score = 0;
        if (fmt->name && short_name && !av_strcasecmp(fmt->name, short_name))
            score += 100;
        if (fmt->mime_type && mime_type && !strcmp(fmt->mime_type, mime_type))
            score += 10;
        if (filename && fmt->extensions &&
            av_match_ext(filename, fmt->extensions)) {
            score += 5;
        }
        if (score > score_max) {
            score_max = score;
            fmt_found = fmt;
        }
    }
    return fmt_found;
}

enum AVCodecID av_guess_codec(AVOutputFormat *fmt, const char *short_name,
                              const char *filename, const char *mime_type,
                              enum AVMediaType type)
{
    if (type == AVMEDIA_TYPE_VIDEO) {
        enum AVCodecID codec_id = AV_CODEC_ID_NONE;

#if CONFIG_IMAGE2_MUXER
        if (!strcmp(fmt->name, "image2") || !strcmp(fmt->name, "image2pipe")) {
            codec_id = ff_guess_image2_codec(filename);
        }
#endif
        if (codec_id == AV_CODEC_ID_NONE)
            codec_id = fmt->video_codec;
        return codec_id;
    } else if (type == AVMEDIA_TYPE_AUDIO)
        return fmt->audio_codec;
    else if (type == AVMEDIA_TYPE_SUBTITLE)
        return fmt->subtitle_codec;
    else
        return AV_CODEC_ID_NONE;
}

AVInputFormat *av_find_input_format(const char *short_name)
{
    AVInputFormat *fmt = NULL;
    while ((fmt = av_iformat_next(fmt)))
        if (match_format(short_name, fmt->name))
            return fmt;
    return NULL;
}

AVInputFormat *av_probe_input_format2(AVProbeData *pd, int is_opened,
                                      int *score_max)
{
    AVProbeData lpd = *pd;
    AVInputFormat *fmt1 = NULL, *fmt;
    int score, id3 = 0;

    if (lpd.buf_size > 10 && ff_id3v2_match(lpd.buf, ID3v2_DEFAULT_MAGIC)) {
        int id3len = ff_id3v2_tag_len(lpd.buf);
        if (lpd.buf_size > id3len + 16) {
            lpd.buf      += id3len;
            lpd.buf_size -= id3len;
        }
        id3 = 1;
    }

    fmt = NULL;
    while ((fmt1 = av_iformat_next(fmt1))) {
        if (!is_opened == !(fmt1->flags & AVFMT_NOFILE))
            continue;
        score = 0;
        if (fmt1->read_probe) {
            score = fmt1->read_probe(&lpd);
        } else if (fmt1->extensions) {
            if (av_match_ext(lpd.filename, fmt1->extensions))
                score = AVPROBE_SCORE_EXTENSION;
        }
        if (score > *score_max) {
            *score_max = score;
            fmt        = fmt1;
        } else if (score == *score_max)
            fmt = NULL;
    }

    // A hack for files with huge id3v2 tags -- try to guess by file extension.
    if (!fmt && is_opened && *score_max < AVPROBE_SCORE_EXTENSION / 2) {
        while ((fmt = av_iformat_next(fmt)))
            if (fmt->extensions &&
                av_match_ext(lpd.filename, fmt->extensions)) {
                *score_max = AVPROBE_SCORE_EXTENSION / 2;
                break;
            }
    }

    if (!fmt && id3 && *score_max < AVPROBE_SCORE_EXTENSION / 2 - 1) {
        while ((fmt = av_iformat_next(fmt)))
            if (fmt->extensions && av_match_ext("mp3", fmt->extensions)) {
                *score_max = AVPROBE_SCORE_EXTENSION / 2 - 1;
                break;
            }
    }

    return fmt;
}

AVInputFormat *av_probe_input_format(AVProbeData *pd, int is_opened)
{
    int score = 0;
    return av_probe_input_format2(pd, is_opened, &score);
}

/* size of probe buffer, for guessing file type from file contents */
#define PROBE_BUF_MIN 2048
#define PROBE_BUF_MAX (1 << 20)

int av_probe_input_buffer(AVIOContext *pb, AVInputFormat **fmt,
                          const char *filename, void *logctx,
                          unsigned int offset, unsigned int max_probe_size)
{
    AVProbeData pd = { filename ? filename : "" };
    uint8_t *buf = NULL;
    int ret = 0, probe_size;

    if (!max_probe_size)
        max_probe_size = PROBE_BUF_MAX;
    else if (max_probe_size > PROBE_BUF_MAX)
        max_probe_size = PROBE_BUF_MAX;
    else if (max_probe_size < PROBE_BUF_MIN)
        return AVERROR(EINVAL);

    if (offset >= max_probe_size)
        return AVERROR(EINVAL);
    avio_skip(pb, offset);
    max_probe_size -= offset;

    for (probe_size = PROBE_BUF_MIN; probe_size <= max_probe_size && !*fmt;
         probe_size = FFMIN(probe_size << 1,
                            FFMAX(max_probe_size, probe_size + 1))) {
        int score = probe_size < max_probe_size ? AVPROBE_SCORE_MAX / 4 : 0;

        /* Read probe data. */
        if ((ret = av_reallocp(&buf, probe_size + AVPROBE_PADDING_SIZE)) < 0)
            return ret;
        if ((ret = avio_read(pb, buf + pd.buf_size,
                             probe_size - pd.buf_size)) < 0) {
            /* Fail if error was not end of file, otherwise, lower score. */
            if (ret != AVERROR_EOF) {
                av_free(buf);
                return ret;
            }
            score = 0;
            ret   = 0;          /* error was end of file, nothing read */
        }
        pd.buf_size += ret;
        pd.buf       = buf;

        memset(pd.buf + pd.buf_size, 0, AVPROBE_PADDING_SIZE);

        /* Guess file format. */
        *fmt = av_probe_input_format2(&pd, 1, &score);
        if (*fmt) {
            /* This can only be true in the last iteration. */
            if (score <= AVPROBE_SCORE_MAX / 4) {
                av_log(logctx, AV_LOG_WARNING,
                       "Format detected only with low score of %d, "
                       "misdetection possible!\n", score);
            } else
                av_log(logctx, AV_LOG_DEBUG,
                       "Probed with size=%d and score=%d\n", probe_size, score);
        }
    }

    if (!*fmt) {
        av_free(buf);
        return AVERROR_INVALIDDATA;
    }

    /* Rewind. Reuse probe buffer to avoid seeking. */
    if ((ret = ffio_rewind_with_probe_data(pb, buf, pd.buf_size)) < 0)
        av_free(buf);

    return ret;
}