[Ffmpeg-devel] Re: ffmpeg/rtsp - dropped videoframes

[Clemens Fischer]

Michael Niedermayer <michaelni <at> gmx.at> writes:

> 
> Hi
> 
> On Tue, Dec 05, 2006 at 04:21:19PM +0100, Clemens Fischer wrote:
> > Hi,
> > 
> >  
> > 
> > I'm using ffmpeg to transcode the video stream of a network camera but the
> > resulting video is not useable because according to the verbose output
> > almost all frames are dropped.
> [...]
> > *** 8 dup!
> > 
> > *** drop!
> [...]
> > *** drop!10 q=2.0 size=      62kB time=0.4 bitrate=1410.8kbits/s dup=9
> > drop=19    
> > 
> > *** drop!
> > 
> > *** drop!
> > 
> > *** drop!
> > 
> > *** drop!
> > 
> > *** drop!10 q=2.0 size=      62kB time=0.4 bitrate=1410.8kbits/s dup=9
> > drop=24    
> > 
> > *** drop!
> > 
> > frame=   11 q=2.1 Lsize=     120kB time=0.4 bitrate=2457.6kbits/s dup=9
> > drop=26
> [...]
> > . the question is now where the problem could be located (rtsp stream, sdp
> > and/or ffmpeg). For the moment I totally lost because I have no idea how to
> > fix this problem but maybe you could provide me some hint(s), because with
> > VLC and realplayer everything works pretty well.
> 
> the whole looks like theres something wrong with the timestamps ...
> 
> [...]

Hi,

thank you for hint because now I'm a step further.
As there is a connex between the timestamp and the samplerate might it be 
possible that ffmpeg is not corretly recognizing "sdp a=rtpmap:97 MP4V-
ES/1000" and using the default sample rate of 90000
(http://www.iana.org/assignments/rtp-parameters) which leads to dropped 
packets frames?

So what could be the next steps - updating "AVRtpPayloadType_t 
AVRtpPayloadTypes[]=...." in "rtp.h" - etc ...
Please provide help as this is the frist time I have to deal with such an 
issue.

thank you
Clemens

PS:
If I add a quick and dirty timestamp correction at line 728 of "rtp.c":
timestamp = (timestamp/14)*90000; // Calc approx. (corr.) timestamp
it is working (allmost) fine.