Hi ,
my team recently had to abandon switching to using FFmpeg from specific decoder
implementations (NvDEC, Intel Media SDK , IPP and quite a few codec specific
decoders) because of big performance issues because of the way FFmpeg works…..
or at least we think it is (we’re FFmpeg noobs 😃 )
It's actually an issue we also had with Intel Media SDK, leading us to pay
Intel to extend Media SDK to do what we needed.
Our product is a video surveillance system, and that means we have to decode a
LOT of video streams simultaneously.
For motion detection we want to only decode keyframes, and skip P and B frames
, and that works fine with FFmpeg most of the time, except for when the video
stream contains B frames.
Without B-Frames it’s really simple (simplified pseudocode) :
while(true)
{
receiveStreamCompleteFrame();
If(KeyFrame)
{
avcodec_send_packet();
if(avcodec_receive_frame()==0)
{
// do motion detection
}
}
}
But! with B Frames FFmpeg doesn’t return keyframes when they are decoded, they
are kept, and we can’t seem to flush them out. avcodec_flush_buffers allow us
to continue to next keyframe, but it doesn’t seem to give us the keyframe we
just gave to FFmpeg with avcodec_send_packet.
while(true)
{
receiveStreamCompleteFrame();
If(KeyFrame)
{
avcodec_send_packet();
if(avcodec_receive_frame()==0)
{
// do motion detection
}
Else
{
avcodec_flush_buffers();
if(avcodec_receive_frame()==0)
{
// do motion detection
}
}
}
}
Calling avcodec_receive_frame after calling avcodec_flush_buffer results in -11
and no frame
is there anyway around this ? And if not, could FFmpeg be made to have this
functionality ?
I tried contacting one of the FFmpeg consultants from
https://ffmpeg.org/consulting.html but never got a response
Michael Bodenhoff
Principal Software Engineer
FT01
Email: m...@milestone.dk
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