[FFmpeg-devel] eval lavfi filter

[Víctor Paesa]

Hi,

Michael Niedermayer said:
> On Wed, Feb 25, 2009 at 11:16:55PM +0100, V?ctor Paesa wrote:
>> Hi,
>>
>> Michael Niedermayer said:
>> > On Wed, Feb 25, 2009 at 01:04:15PM +0100, V?ctor Paesa wrote:
>> >> Hi,
>> >> Michael Niedermayer said:
>> >> > On Wed, Feb 25, 2009 at 09:07:57AM +0100, V?ctor Paesa wrote:
>> >> >> Hi,
>> >> >>
>> >> >> Michael Niedermayer said:
>> >> >> > On Tue, Feb 24, 2009 at 11:56:54PM +0100, Stefano Sabatini
>> wrote:
>> >> >> >> On date Tuesday 2009-02-24 23:26:23 +0100, Michael
>> Niedermayer
>> >> >> encoded:
>> >> >> >> > On Tue, Feb 24, 2009 at 10:39:22PM +0100, Stefano Sabatini
>> >> wrote:
>> >> >> >> > > Hi.
>> >> >> >> > >
>> >> >> >> > > On date Tuesday 2009-01-20 09:37:21 +0100, V?ctor Paesa
>> >> >> encoded:
>> >> >> >> > > > There is also a problem for filters that remove frames,
>> as
>> >> >> >> ffmpeg uses/expects the fps of the input video (instead of
>> the
>> >> >> filtered one) and generates duplicated frames to reach that.
>> >> >> >> >
>> >> >> >> > ffmpeg should not duplicate frames anymore if the container
>> >> can
>> >> >> >> handle it
>> >> >> >>
>> >> >> >> Could someone give some more hints about this?
>> >> >> >
>> >> >> > just try the example that caused frame duplication and check
>> the
>> >> >> resulting file, avi/mov/mp4/nut should have no duplicate frames
>> >> anymore. feedback and bugreports welcome ...
>> >> >> >
>> >> >> >
>> >> >> >>
>> >> >> >> Also I suppose this is not necessarily a lavfi-related issue,
>> >> >> right?
>> >> >> >
>> >> >> > no
>> >> >>
>> >> >> Right, I was able to trace it (but not able to fix) to ffmpeg.c,
>> it
>> >> seems that do_video() is duplicating frames. Maybe adding a new
>> "-vsync 3" that would not perfom any frame rate duplication?
>> >> >
>> >> > just tried
>> >> > ffmpeg -v 9 -i matrixbench_mpeg2.mpg -r 90 test.avi
>> >> >
>> >> > no duplicated frames are generated and considering you provide
>> not a
>> >> single word of a hint of what you did or what did not work i cant
>> help
>> >>
>> >> I'm sorry, I answered without reading your commit 17555, please
>> discard my comments.
>> >>
>> >> Some tests on r17555:
>> >>
>> >> in.avi > >>
>> http://samples.mplayerhq.hu/avi/fpstest/gwl-bounce-sample-25fps.avi
>> that is 60 seconds long and has 1500 frames.
>> >>
>> >> $ ffmpeg  -i in.avi -vfilters fps=1 -y -an out_fps1.avi
>> >> FFmpeg version SVN-r17555, Copyright (c) 2000-2009 Fabrice Bellard,
>> et al.
>> >>   configuration: --enable-shared --disable-static --cpu=prescott
>> >> --extra-cflags=-DX_DISPLAY_MISSING -I/usr/local/include -include
>> llrint.h --extra-ldflags=-L/usr/local/lib --extra-libs=-l llrint
>> --enable-gpl --enable-nonfree --enable-libamr-nb --enable-libamr-wb
>> --enable-swscale --enable-avfilter --enable-avfilter-lavf
>> >> --enable-pthreads --enable-avisynth --enable-bzlib --enable-libfaac
>> --enable-libgsm --enable-libmp3lame --enable-libtheora
>> >> --enable-libx264 --enable-zlib --build-suffix=-SVN
>> >>   libavutil     49.15. 0 / 49.15. 0
>> >>   libavcodec    52.18. 0 / 52.18. 0
>> >>   libavformat   52.29. 2 / 52.29. 2
>> >>   libavdevice   52. 1. 0 / 52. 1. 0
>> >>   libavfilter    0. 4. 0 /  0. 4. 0
>> >>   libswscale     0. 7. 1 /  0. 7. 1
>> >>   built on Feb 25 2009 11:41:58, gcc: 4.2.4
>> >>
>> >> Seems stream 0 codec frame rate differs from container frame rate:
>> 30000.00 (30000/1) -> 25.00 (25/1)
>> >> Input #0, avi, from 'in.avi':
>> >>   Duration: 00:01:00.03, start: 0.000000, bitrate: 822 kb/s
>> >>     Stream #0.0: Video: mpeg4, yuv420p, 640x352 [PAR 1:1 DAR
>> 20:11],
>> >> 25
>> >> tbr, 25 tbn, 30k tbc
>> >>     Stream #0.1: Audio: mp3, 22050 Hz, stereo, s16, 56 kb/s
>> >> Output #0, avi, to 'out_fps1.avi':
>> >>     Stream #0.0: Video: mpeg4, yuv420p, 640x352 [PAR 1:1 DAR
>> 20:11],
>> >> q=2-31, 200 kb/s, 90k tbn, 25 tbc
>> >> Stream mapping:
>> >>   Stream #0.0 -> #0.0
>> >> Press [q] to stop encoding
>> >> frame=   60 fps= 35 q=6.9 Lsize=     292kB time=59.04 bitrate> >>
>> 40.5kbits/s video:252kB audio:0kB global headers:0kB muxing
>> overhead 16.000823%
>> >>
>> >>
>> >> The out_fps1.avi has 60 frames, as expected, but VirtualDub
>> believes has 1476 frames due to the 25 tbc probably. GSpot reports
>> 60 frames. ffmpeg is also confused and ffmpeg -i out_fps1.avi
>> out%04d.png produces 1475 PNGs.
>> >>
>> >>
>> >> ffmpeg  -i in.avi -vfilters fps=1 -r 1  -y -an out_fps1_r1.avi
>> >>
>> >> The out_fps1_r1.avi has 60 frames, works fine in VirtualDub, GSpot,
>> ffmpeg.
>> >
>> > all mostly as expected, did you expect anything else?
>>
>> Well, since avfilters may drop/add frames and alter timestamps, there
>> should be some way to tell ffmpeg to avoid sync'ing against the
>> original input stream.
>
> i dont understand what you mean
> if you want the timestamps of future frames decreased by "1" after a
> droped frame, the drop filter surely can adjust the timestamps.
> if its not that i dont understand what what you try to explain

I'll try to prepare such drop filter to explore better this
(please do not understand that as some futile attempt to delay avfilter).

>> -r is a way, but it then forces a fixed rate.
>
> there is always some rate, that may be 1/10000000 or 1/25 but there is
> always one.
> -r does not force fixed fps
> -r X -vsync 1 does and vsync 1 was default a long time ago, vsync
> switched to -1 as default and the behavior of -1 changed recently

Thanks for your explanation.

Regards,
V?ctor