From: Matthieu Bouron <matthieu.bou...@stupeflix.com>
Avoid decoding twice images such as jpeg and png, once in the
avformat_find_stream_info and once when the actual decode is made.
The decoder must honor the skip_frame option in order to skip
decoding. For now the AVDISCARD_ALL flag is only set for the mjpeg and
png decoders.
---
libavformat/utils.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/libavformat/utils.c b/libavformat/utils.c
index 689473e..67dfffc 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -2676,11 +2676,16 @@ static int has_codec_parameters(AVStream *st, const
char **errmsg_ptr)
static int try_decode_frame(AVFormatContext *s, AVStream *st, AVPacket *avpkt,
AVDictionary **options)
{
+ int i;
const AVCodec *codec;
int got_picture = 1, ret = 0;
AVFrame *frame = av_frame_alloc();
AVSubtitle subtitle;
AVPacket pkt = *avpkt;
+ int skip_frame;
+ static const enum AVCodecID no_decode_codecs[] = {
+ AV_CODEC_ID_MJPEG, AV_CODEC_ID_PNG,
+ };
if (!frame)
return AVERROR(ENOMEM);
@@ -2719,6 +2724,14 @@ static int try_decode_frame(AVFormatContext *s, AVStream
*st, AVPacket *avpkt,
goto fail;
}
+ skip_frame = st->codec->skip_frame;
+ for (i = 0; i < FF_ARRAY_ELEMS(no_decode_codecs); i++) {
+ if (st->codec->codec_id == no_decode_codecs[i]) {
+ st->codec->skip_frame = AVDISCARD_ALL;
+ break;
+ }
+ }
+
while ((pkt.size > 0 || (!pkt.data && got_picture)) &&
ret >= 0 &&
(!has_codec_parameters(st, NULL) ||
!has_decode_delay_been_guessed(st) ||
@@ -2753,6 +2766,8 @@ static int try_decode_frame(AVFormatContext *s, AVStream
*st, AVPacket *avpkt,
if (!pkt.data && !got_picture)
ret = -1;
+ st->codec->skip_frame = skip_frame;
+
fail:
av_frame_free(&frame);
return ret;
--
2.6.1
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