[FFmpeg-user] How to drop every Nth frame?

[Andrey Aleksandrovich]

The new issue. How to use several filters with "select"?
$ ffmpeg -y -r 372 -i mark.avi -i pcm.wav -c:v ffvhuff -filter:v
select=mod'(n\,372)',crop=in_w-20::11:,scale=320:240 -r 371 -c:a copy
fin.avi
ffmpeg version 1.2.3 Copyright (c) 2000-2013 the FFmpeg developers
  built on Sep 21 2013 15:25:21 with gcc 4.6.3 (Gentoo Hardened 4.6.3
p1.13, pie-0.5.2)
  configuration: --prefix=/usr --libdir=/usr/lib64
--shlibdir=/usr/lib64 --mandir=/usr/share/man --enable-shared
--cc=x86_64-pc-linux-gnu-gcc --cxx=x86_64-pc-linux-gnu-g++
--ar=x86_64-pc-linux-gnu-ar --optflags='-O2 -pipe -march=native'
--extra-cflags='-O2 -pipe -march=native' --extra-cxxflags='-O2 -pipe
-march=native' --disable-static --enable-gpl --enable-postproc
--enable-avfilter --enable-avresample --disable-stripping
--enable-version3 --disable-indev=v4l2 --disable-indev=oss
--disable-indev=jack --disable-outdev=oss --enable-version3
--enable-bzlib --disable-runtime-cpudetect --disable-debug
--disable-doc --disable-gnutls --enable-hardcoded-tables
--enable-iconv --disable-network --disable-openssl --enable-ffplay
--disable-vaapi --enable-vdpau --enable-zlib --disable-libvo-aacenc
--enable-libvo-amrwbenc --enable-libmp3lame --disable-libfdk-aac
--disable-libaacplus --disable-libfaac --enable-libtheora
--disable-libtwolame --enable-libx264 --enable-libxvid
--disable-libcdio --disable-libiec61883 --disabl  libavutil      52.
18.100 / 52. 18.100
  libavcodec     54. 92.100 / 54. 92.100
  libavformat    54. 63.104 / 54. 63.104
  libavdevice    54.  3.103 / 54.  3.103
  libavfilter     3. 42.103 /  3. 42.103
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
Input #0, avi, from 'mark.avi':
  Duration: 01:33:34.40, start: 0.000000, bitrate: 9758 kb/s
    Stream #0:0: Video: ffvhuff (FFVH / 0x48564646), yuv420p, 320x240,
20 tbr, 20 tbn, 20 tbc
[wav @ 0x5341fc6c50] max_analyze_duration 5000000 reached at 5013333
microseconds
Guessed Channel Layout for  Input Stream #1.0 : stereo
Input #1, wav, from 'pcm.wav':
  Metadata:
    encoder         : Lavf54.63.104 (libsndfile-1.0.25)
  Duration: 01:33:20.07, bitrate: 1536 kb/s
    Stream #1:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz,
stereo, s16, 1536 kb/s
[Parsed_crop_1 @ 0x534205df00] [Eval @ 0x3d91e33f940] Undefined
constant or missing '(' in ''
Error when evaluating the expression ''
[Parsed_select_0 @ 0x534204d930] Failed to configure input pad on Parsed_crop_1
Error opening filters!
$

What's wrong with the syntax?

On 9/21/13, Andrey Aleksandrovich <andrey.aleksandrovich at googlemail.com> wrote:
> Sorry to You, my fault.
> All is working now.
>
> On 9/21/13, Andrey Aleksandrovich <andrey.aleksandrovich at googlemail.com>
> wrote:
>> I am sorry but it doesn't cut any frames at all.
>> ffmpeg -y -i original-5614-frames.avi -filter:v "select='mod(n,24)'"
>> out.avi
>>
>> The original video is 5614 frames and the output video is 5614 ones.
>> I expect that output must be 5381 frames (I need to cut/drop 233
>> frames - every 24th from 5614).
>>
>> On 9/21/13, Sam Logan <shapableline at gmail.com> wrote:
>>> On 9/21/13, Andrey Aleksandrovich <andrey.aleksandrovich at googlemail.com>
>>> wrote:
>>>> oh, thanks, but I can't understand syntax of select filer:
>>>> Example from manual:
>>>> # select one frame every 100
>>>> select='not(mod(n,100))'
>>>>
>>>> But how to set - "select 23 frames every 24"?
>>>
>>> mod() is the modulus function. So mod(n, 100) returns positive for any
>>> value of n except for multiples of 100, so Boolean negation of that
>>> will return false for everything except multiples of 100, thereby
>>> selecting one frame per hundred. So to select 23 frames per 24, do:
>>>
>>> select='mod(n,24)'
>>> _______________________________________________
>>> ffmpeg-user mailing list
>>> ffmpeg-user at ffmpeg.org
>>> http://ffmpeg.org/mailman/listinfo/ffmpeg-user
>>>
>>
>