rtmpproto: Clarify a comment

[ffmpeg] / libavformat / flvdec.c

diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
index 56c932c77cd7e1ebcad4506be391bd15ba451e9e..0167d17c701db9a2e1b2bd39b3a94b77ba9308b2 100644 (file)
--- a/libavformat/flvdec.c
+++ b/libavformat/flvdec.c
@@ -717,7 +717,7 @@ static int flv_data_packet(AVFormatContext *s, AVPacket *pkt,
     if (i == s->nb_streams) {
         st = create_stream(s, AVMEDIA_TYPE_DATA);
         if (!st)
-            return AVERROR_INVALIDDATA;
+            return AVERROR(ENOMEM);
         st->codec->codec_id = AV_CODEC_ID_TEXT;
     }
 
@@ -817,9 +817,12 @@ skip:
                     break;
             }
         }
-        if (i == s->nb_streams)
+        if (i == s->nb_streams) {
             st = create_stream(s, is_audio ? AVMEDIA_TYPE_AUDIO
                                            : AVMEDIA_TYPE_VIDEO);
+            if (!st)
+                return AVERROR(ENOMEM);
+        }
         av_dlog(s, "%d %X %d \n", is_audio, flags, st->discard);
 
         if ((flags & FLV_VIDEO_FRAMETYPE_MASK) == FLV_FRAME_KEY ||
@@ -842,9 +845,13 @@ skip:
     if (s->pb->seekable && (!s->duration || s->duration == AV_NOPTS_VALUE)) {
         int size;
         const int64_t pos   = avio_tell(s->pb);
+        // Read the last 4 bytes of the file, this should be the size of the
+        // previous FLV tag. Use the timestamp of its payload as duration.
         const int64_t fsize = avio_size(s->pb);
         avio_seek(s->pb, fsize - 4, SEEK_SET);
         size = avio_rb32(s->pb);
+        // Seek to the start of the last FLV tag at position (fsize - 4 - size)
+        // but skip the byte indicating the type.
         avio_seek(s->pb, fsize - 3 - size, SEEK_SET);
         if (size == avio_rb24(s->pb) + 11) {
             uint32_t ts = avio_rb24(s->pb);
@@ -879,6 +886,7 @@ skip:
         } else {
             AVCodecContext ctx;
             ctx.sample_rate = sample_rate;
+            ctx.bits_per_coded_sample = bits_per_coded_sample;
             flv_set_audio_codec(s, st, &ctx, flags & FLV_AUDIO_CODECID_MASK);
             sample_rate = ctx.sample_rate;
         }