apng: use side data to pass extradata to muxer

This fixes creating apng files, which is broken since commit
5ef1959080.

Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

libavcodec/pngenc.c

@@ -68,6 +68,9 @@ typedef struct PNGEncContext {
     // APNG
     uint32_t palette_checksum;   // Used to ensure a single unique palette
     uint32_t sequence_number;
+    int extra_data_updated;
+    uint8_t *extra_data;
+    int extra_data_size;
 
     AVFrame *prev_frame;
     AVFrame *last_frame;
@@ -870,15 +873,15 @@ static int encode_apng(AVCodecContext *avctx, AVPacket *pkt,
         if (!pict)
             return AVERROR(EINVAL);
 
-        s->bytestream = avctx->extradata = av_malloc(FF_MIN_BUFFER_SIZE);
-        if (!avctx->extradata)
+        s->bytestream = s->extra_data = av_malloc(FF_MIN_BUFFER_SIZE);
+        if (!s->extra_data)
             return AVERROR(ENOMEM);
 
         ret = encode_headers(avctx, pict);
         if (ret < 0)
             return ret;
 
-        avctx->extradata_size = s->bytestream - avctx->extradata;
+        s->extra_data_size = s->bytestream - s->extra_data;
 
         s->last_frame_packet = av_malloc(max_packet_size);
         if (!s->last_frame_packet)
@@ -917,6 +920,13 @@ static int encode_apng(AVCodecContext *avctx, AVPacket *pkt,
     if (s->last_frame) {
         uint8_t* last_fctl_chunk_start = pkt->data;
         uint8_t buf[26];
+        if (!s->extra_data_updated) {
+            uint8_t *side_data = av_packet_new_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA, s->extra_data_size);
+            if (!side_data)
+                return AVERROR(ENOMEM);
+            memcpy(side_data, s->extra_data, s->extra_data_size);
+            s->extra_data_updated = 1;
+        }
 
         AV_WB32(buf + 0, s->last_frame_fctl.sequence_number);
         AV_WB32(buf + 4, s->last_frame_fctl.width);
@@ -1093,6 +1103,8 @@ static av_cold int png_enc_close(AVCodecContext *avctx)
     av_frame_free(&s->last_frame);
     av_frame_free(&s->prev_frame);
     av_freep(&s->last_frame_packet);
+    av_freep(&s->extra_data);
+    s->extra_data_size = 0;
     return 0;
 }
 

libavformat/apngenc.c

@@ -44,6 +44,9 @@ typedef struct APNGMuxContext {
     AVRational prev_delay;
 
     int framerate_warned;
+
+    uint8_t *extra_data;
+    int extra_data_size;
 } APNGMuxContext;
 
 static uint8_t *apng_find_chunk(uint32_t tag, uint8_t *buf, size_t length)
@@ -101,15 +104,27 @@ static int apng_write_header(AVFormatContext *format_context)
     return 0;
 }
 
-static void flush_packet(AVFormatContext *format_context, AVPacket *packet)
+static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
 {
     APNGMuxContext *apng = format_context->priv_data;
     AVIOContext *io_context = format_context->pb;
     AVStream *codec_stream = format_context->streams[0];
-    AVCodecParameters *codec_par = codec_stream->codecpar;
+    uint8_t *side_data = NULL;
+    int side_data_size = 0;
 
     av_assert0(apng->prev_packet);
 
+    side_data = av_packet_get_side_data(apng->prev_packet, AV_PKT_DATA_NEW_EXTRADATA, &side_data_size);
+
+    if (side_data_size) {
+        av_freep(&apng->extra_data);
+        apng->extra_data = av_mallocz(side_data_size + AV_INPUT_BUFFER_PADDING_SIZE);
+        if (!apng->extra_data)
+            return AVERROR(ENOMEM);
+        apng->extra_data_size = side_data_size;
+        memcpy(apng->extra_data, side_data, apng->extra_data_size);
+    }
+
     if (apng->frame_number == 0 && !packet) {
         uint8_t *existing_acTL_chunk;
         uint8_t *existing_fcTL_chunk;
@@ -117,13 +132,13 @@ static void flush_packet(AVFormatContext *format_context, AVPacket *packet)
         av_log(format_context, AV_LOG_INFO, "Only a single frame so saving as a normal PNG.\n");
 
         // Write normal PNG headers without acTL chunk
-        existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), codec_par->extradata, codec_par->extradata_size);
+        existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
         if (existing_acTL_chunk) {
             uint8_t *chunk_after_acTL = existing_acTL_chunk + AV_RB32(existing_acTL_chunk) + 12;
-            avio_write(io_context, codec_par->extradata, existing_acTL_chunk - codec_par->extradata);
-            avio_write(io_context, chunk_after_acTL, codec_par->extradata + codec_par->extradata_size - chunk_after_acTL);
+            avio_write(io_context, apng->extra_data, existing_acTL_chunk - apng->extra_data);
+            avio_write(io_context, chunk_after_acTL, apng->extra_data + apng->extra_data_size - chunk_after_acTL);
         } else {
-            avio_write(io_context, codec_par->extradata, codec_par->extradata_size);
+            avio_write(io_context, apng->extra_data, apng->extra_data_size);
         }
 
         // Write frame data without fcTL chunk
@@ -142,9 +157,9 @@ static void flush_packet(AVFormatContext *format_context, AVPacket *packet)
             uint8_t *existing_acTL_chunk;
 
             // Write normal PNG headers
-            avio_write(io_context, codec_par->extradata, codec_par->extradata_size);
+            avio_write(io_context, apng->extra_data, apng->extra_data_size);
 
-            existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), codec_par->extradata, codec_par->extradata_size);
+            existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
             if (!existing_acTL_chunk) {
                 uint8_t buf[8];
                 // Write animation control header
@@ -195,11 +210,13 @@ static void flush_packet(AVFormatContext *format_context, AVPacket *packet)
     av_packet_unref(apng->prev_packet);
     if (packet)
         av_copy_packet(apng->prev_packet, packet);
+    return 0;
 }
 
 static int apng_write_packet(AVFormatContext *format_context, AVPacket *packet)
 {
     APNGMuxContext *apng = format_context->priv_data;
+    int ret;
 
     if (!apng->prev_packet) {
         apng->prev_packet = av_malloc(sizeof(*apng->prev_packet));
@@ -208,7 +225,9 @@ static int apng_write_packet(AVFormatContext *format_context, AVPacket *packet)
 
         av_copy_packet(apng->prev_packet, packet);
     } else {
-        flush_packet(format_context, packet);
+        ret = flush_packet(format_context, packet);
+        if (ret < 0)
+            return ret;
     }
 
     return 0;
@@ -219,10 +238,13 @@ static int apng_write_trailer(AVFormatContext *format_context)
     APNGMuxContext *apng = format_context->priv_data;
     AVIOContext *io_context = format_context->pb;
     uint8_t buf[8];
+    int ret;
 
     if (apng->prev_packet) {
-        flush_packet(format_context, NULL);
+        ret = flush_packet(format_context, NULL);
         av_freep(&apng->prev_packet);
+        if (ret < 0)
+            return ret;
     }
 
     apng_write_chunk(io_context, MKBETAG('I', 'E', 'N', 'D'), NULL, 0);
@@ -235,6 +257,9 @@ static int apng_write_trailer(AVFormatContext *format_context)
         apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
     }
 
+    av_freep(&apng->extra_data);
+    apng->extra_data = 0;
+
     return 0;
 }