[FFmpeg-devel] [PATCH v3] avformat/flvdec: move read fourcc output before flv_same_video_codec

[Steven Liu <lq@chinaffmpeg.org>]

read fourcc for video codec after VideoTagHeader read.
passed as parameter to flv_same_video_codec.

Signed-off-by: Steven Liu <lq@chinaffmpeg.org>
---
 libavformat/flvdec.c | 38 ++++++++++++++++++++++----------------
 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
index 3fe21622f7..e3cceba5d0 100644
--- a/libavformat/flvdec.c
+++ b/libavformat/flvdec.c
@@ -35,6 +35,7 @@
 #include "libavutil/intreadwrite.h"
 #include "libavutil/mathematics.h"
 #include "avformat.h"
+#include "avio_internal.h"
 #include "demux.h"
 #include "internal.h"
 #include "flv.h"
@@ -304,27 +305,22 @@ static void flv_set_audio_codec(AVFormatContext *s, AVStream *astream,
     }
 }
 
-static int flv_same_video_codec(AVFormatContext *s, AVCodecParameters *vpar, int flags)
+static int flv_same_video_codec(AVFormatContext *s, AVCodecParameters *vpar, uint32_t extent_codec_id, int flags)
 {
     int flv_codecid = flags & FLV_VIDEO_CODECID_MASK;
-    FLVContext *flv = s->priv_data;
 
     if (!vpar->codec_id && !vpar->codec_tag)
         return 1;
 
-    if (flv->exheader) {
-        uint8_t *codec_id_str = (uint8_t *)s->pb->buf_ptr;
-        uint32_t codec_id = codec_id_str[3] | codec_id_str[2] << 8 | codec_id_str[1] << 16 | codec_id_str[0] << 24;
-        switch(codec_id) {
-            case MKBETAG('h', 'v', 'c', '1'):
-                return vpar->codec_id == AV_CODEC_ID_HEVC;
-            case MKBETAG('a', 'v', '0', '1'):
-                return vpar->codec_id == AV_CODEC_ID_AV1;
-            case MKBETAG('v', 'p', '0', '9'):
-                return vpar->codec_id == AV_CODEC_ID_VP9;
-            default:
-                break;
-        }
+    switch(extent_codec_id) {
+        case MKBETAG('h', 'v', 'c', '1'):
+            return vpar->codec_id == AV_CODEC_ID_HEVC;
+        case MKBETAG('a', 'v', '0', '1'):
+            return vpar->codec_id == AV_CODEC_ID_AV1;
+        case MKBETAG('v', 'p', '0', '9'):
+            return vpar->codec_id == AV_CODEC_ID_VP9;
+        default:
+            break;
     }
 
     switch (flv_codecid) {
@@ -1065,6 +1061,7 @@ static int flv_read_packet(AVFormatContext *s, AVPacket *pkt)
     AVStream *st    = NULL;
     int last = -1;
     int orig_size;
+    uint32_t extent_codec_id = 0;
 
 retry:
     /* pkt size is repeated at end. skip it */
@@ -1117,6 +1114,15 @@ retry:
          * */
         flv->exheader = (flags >> 7) & 1;
         size--;
+        if (flv->exheader) {
+            int ensure_seekback_status = ffio_ensure_seekback(s->pb, 4);
+            if (ensure_seekback_status < 0) {
+                av_log(s, AV_LOG_WARNING, "Could not ensure seekback\n");
+                return ensure_seekback_status;
+            }
+            extent_codec_id = avio_rb32(s->pb);
+            avio_seek(s->pb, -4, SEEK_CUR);
+        }
         if ((flags & FLV_VIDEO_FRAMETYPE_MASK) == FLV_FRAME_VIDEO_INFO_CMD)
             goto skip;
     } else if (type == FLV_TAG_TYPE_META) {
@@ -1174,7 +1180,7 @@ skip:
                 break;
         } else if (stream_type == FLV_STREAM_TYPE_VIDEO) {
             if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO &&
-                (s->video_codec_id || flv_same_video_codec(s, st->codecpar, flags)))
+                (s->video_codec_id || flv_same_video_codec(s, st->codecpar, extent_codec_id, flags)))
                 break;
         } else if (stream_type == FLV_STREAM_TYPE_SUBTITLE) {
             if (st->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE)
-- 
2.40.0

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