The documentation <https://www.ffmpeg.org/doxygen/trunk/group__lavf__decoding.html#ga4fdb3084415a82e3810de6ee60e46a61> says "*For video, the packet contains exactly one frame.*" I used this <http://dranger.com/ffmpeg/> tutorial to understand the flow of what needs to be done. Some of the calls were deprecated so a few google searches got me the replacements. What appears to be happening is those lost frames are just gone...the data isn't being accumulated. Is it possible my av_free_packet call is in a bad spot?
On Tue, Jul 22, 2014 at 10:58 AM, cyril poulet <[email protected] > wrote: > what av_read_frame does is take some data and fill your packet with it. > There is no guaranty that a full frame is in the packet, or even image data. > avcodec_decode_video2 is the only way to know if you have decoded an image > : you feed it your successive packets, it accumulates data, and tells you > when the data allowed him to successfully decode an image (through > frameFinished) > You should look online for basic examples of how to decode safely vids, > there is in particular a tutorial which introduces the structure SafePacket > (first version has been updated for latest versions of the libs) > > > 2014-07-22 16:49 GMT+02:00 Matt Orlando <[email protected]>: > > Thanks for the response. That's very interesting, though I wonder if it >> could actually be header related. Based on the videos, I know for sure >> there are exactly 64 frames in the first movie, for instance. My >> m_FrameRead is only increased if avcodec_decode_video2 says it was able to >> get a picture. My thinking is that if it was a header that was read, that >> function wouldn't set frameFinished to "true". So av_read_frame hits the >> EOF when my m_FrameRead counter is only 56. >> >> Are you saying that perhaps the av_read_frame is reading a bunch of data >> (header + frames) and my avcodec_decode_video2 says there's no picture >> because there's header data in there. Then a few frames later (or maybe >> next frame), av_read_frame reads more data, now including the 9th 'frame' >> and finally avcodec_decode_video2 decodes and I increment my counter (which >> would be now 1 when I'd want it to be 9). >> >> Thanks for the help! >> -Matt >> >> >> On Tue, Jul 22, 2014 at 8:30 AM, cyril poulet < >> [email protected]> wrote: >> >>> according to the doc, av_read_packet does not check wether the data in >>> the decoded frame is a valid image or not. >>> As it is always the 8 first "frames" missing, I would assume it is the >>> header that gets decoded first. >>> Have you noticed missing images when comparing the first real decoded >>> image and your stream in a player ? >>> >>> >>> 2014-07-21 18:37 GMT+02:00 Matt Orlando <[email protected]>: >>> >>>> Hi folks, >>>> >>>> I'm having some trouble with the decoding of my h.264 movies. I've >>>> tested with different videos, one 64 frames long and another 52 frames >>>> long. In both cases, the first 8 frames (exactly 8) weren't decoding. In >>>> other words, the call to avcodec_decode_video2 returns 0 for the >>>> got_picture variable. I track the frames read and received for our system >>>> and I never get notice that all the frames were read because my counter >>>> doesn't increase for the first 8...however all of the subsequent calls to >>>> av_read_frame return EOF. To prevent any confusion (or perhaps just to add >>>> some context), I need the raw data from each decoded frame since I don't >>>> treat them as a frame to a movie but rather a frame of x,y,z positional >>>> data. >>>> >>>> I work in Unity but made a plugin to communicate with the libraries to >>>> read and decode the h.264 movies. This is our update function: >>>> >>>> bool H264Stream::Update(int desiredFrame) >>>> { >>>> if( desiredFrame <= m_FrameRead ) >>>> return true; >>>> >>>> int frameFinished = 0; >>>> >>>> if( av_read_frame( m_AVFormat, &m_Packet ) >= 0 ) >>>> { >>>> if( m_Packet.stream_index == m_AVStream->index ) >>>> { >>>> av_frame_unref( m_AVFrame ); >>>> avcodec_decode_video2( m_AVContext, m_AVFrame, &frameFinished, >>>> &m_Packet ); >>>> >>>> if( frameFinished != 0 ) >>>> { >>>> sws_scale( m_SwsContext, m_AVFrame->data, >>>> m_AVFrame->linesize, 0, m_AVContext->height, m_Picture->data, >>>> m_Picture->linesize ); >>>> >>>> m_FrameRead++; >>>> >>>> av_free_packet( &m_Packet ); >>>> } >>>> } >>>> } >>>> >>>> return m_FrameRead >= desiredFrame; >>>> } >>>> >>>> >>>> Oh, quick note, this is my first time using these libraries so if >>>> there's something blatantly wrong with how I'm doing this, please let me >>>> know. :) Just keep in mind, it's the full frame of 'raw' data I use >>>> (post-decode) that I pass back into my Unity c# scripts. >>>> >>>> Thanks for the help everyone! >>>> -Matt >>>> >>>> _______________________________________________ >>>> Libav-user mailing list >>>> [email protected] >>>> http://ffmpeg.org/mailman/listinfo/libav-user >>>> >>>> >>> >>> _______________________________________________ >>> Libav-user mailing list >>> [email protected] >>> http://ffmpeg.org/mailman/listinfo/libav-user >>> >>> >> >> _______________________________________________ >> Libav-user mailing list >> [email protected] >> http://ffmpeg.org/mailman/listinfo/libav-user >> >> > > _______________________________________________ > Libav-user mailing list > [email protected] > http://ffmpeg.org/mailman/listinfo/libav-user > >
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