>-----Original Message-----
>From: [email protected]
[mailto:[email protected]] On Behalf Of Jeremy Culver
>Sent: Thursday, May 07, 2009 1:49 PM
>To: Libav* user questions and discussions
>Subject: Re: [libav-user] How do I decode only I-Frames in H.264 in
ffmpeg?
>
>On Thu, May 7, 2009 at 9:35 AM, Rusty Waters <[email protected]>
wrote:
>> Hi All,
>>
>> I am able to easily to decode only I-frames in MEPG-2 with
avctx->skip_frame = AVDISCARD_NONKEY. When I use this flag for decoding
H.264, all frames are decoded.
>> Does anybody know what flags I have to set for H.264 to decode only
>> I-frames. Is this feature broken in H.264?
>>
>> Thanks, Rusty
>>
>>
>>
>
>
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>
>
>How about something like
>
>AVPacket pkt;
>av_init_packet ( &pkt );
>while ( av_read_frame(fmt_ctx, &pkt) >=0 ) {
> if ( decode_keyonly && (pkt.flags & PKT_FLAG_KEY) == 0 )
> continue;
>
> // proceed with avcodec_decode_video
> // ...
>}
>
>
>
>
>
>J.
Thanks very much for writing. I appreciate it. Your solution looks like
a good one, except that my application uses it's own memory
allocation/buffering,
and doesn't use av_read_frame, so pkt.flags won't be set.
For example my call to avcodec_decode_video is:
unsigned char* outputBuffer = (unsigned
char*)obg.Map();
// Did we get a video frame?
int decodedBytes =
_pDecoder->DecodeFrame(videoBuffer,videoBufferSize,outputBuffer,outputBu
fferSize);
........
Where _pDecoder->DecodeFrame is:
int DecoderFFmpeg::DecodeFrame(const unsigned char* pFrameBuffer, const
unsigned int length, unsigned char *pDecodedFrameBuf, unsigned int
DecodedBufSize)
{
if ( (NULL == pFrameBuffer) || (NULL == pDecodedFrameBuf) ||
(length < 1) || (false == _pCtx->bOpened) )
return -1;
int gotPicture = 0;
avcodec_decode_video( _pCtx->pCodecCtx,
_pCtx->pFrame,
&gotPicture,
(unsigned char*)pFrameBuffer,
length);
.............
This is why I was relying on the internal flag of the decoder to get me
what I wanted . When I get a solution to this, I will be glad to put it
back on the
Libav-user site.
Thanks again, Rusty
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