[vlc-devel] Re: [Patch] Allow DV sources to skip frames

[Jean-Paul Saman]

Paul Corke wrote:
> On 22 April 2007 10:24, Jean-Paul Saman wrote:
> 
>> Did you try --sout-transcode-hurry-up ? it drops frames if the CPU
>> can't keep up. Also add --cr-average=1000.
>>
>> Does your problem persist?
> 
> Here is my command line based on your suggestions:
> 
> dvgrab -fmt dv1 --buffers 4 - | \
> vlc -vvv --intf dummy --no-sub-autodetect-file - :demux=rawdv \
> --sout-transcode-hurry-up --cr-average=1000 \
> --sout '#transcode{vcodec=mp2v,vb=6000,acodec=mp2a,ab=192,venc=ffmpeg}:\
> standard{access=http,mux=asf,dst=:5182}'
> 
> It soon goes back to the old behaviour of:

Ok I'll merge your patch.

Gtz,
Jean-Paul Saman.

> 
> [00000357] stream_out_transcode private debug: late picture skipped
> (177860)
> [00000366] main private warning: late buffer for mux input (115597)
> [00000357] stream_out_transcode private debug: late picture skipped
> (168370)
> [00000366] main private warning: late buffer for mux input (123542)
> [00000357] stream_out_transcode private debug: late picture skipped
> (160336)
> [00000366] main private warning: late buffer for mux input (138058)
> [00000357] stream_out_transcode private debug: late picture skipped
> (182837)
> [00000366] main private warning: late buffer for mux input (120597)
> [00000357] stream_out_transcode private debug: late picture skipped
> (173382)
> [00000366] main private warning: late buffer for mux input (128572)
> [00000357] stream_out_transcode private debug: late picture skipped
> (165338)
> [00000366] main private warning: late buffer for mux input (143068)
> 
> which is what I would expect.
> 
> The problem is not that the CPU is dropping frames because it can't
> keep up, it's that the external DV codec box isn't sending 25 frames
> per second, so the demux isn't able to supply enough frames to keep
> the transcode happy.
> 
> mdate()     received from DV    sent to transcode       sent to
> transcode
>                                 original vlc-svn        with patch
> 1           1                   1                       1
> 2           2                   2                       2
> 3           (nothing) 
> 4           4                   3                       4
> 5           5                   4                       5
> 
> In the existing vlc, the "sent to transcode" starts to get
> behind "mdate()" the system drops the frame because it thinks it
> has arrived too late.
> 
> After the patch (and once activated with :rawdv-realtime), the source
> can
> drop frames but the timestamp is always new enough to get through.
> 
> Regards,
> 
> Paul.
> 

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