[FFmpeg-user] Question about tmix filter

[Michael Koch]

Am 06.03.2019 um 20:17 schrieb Paul B Mahol:
> On 3/6/19, Michael Koch <astroelectronic at t-online.de> wrote:
>> Am 06.03.2019 um 17:12 schrieb Paul B Mahol:
>>> On 3/6/19, Michael Koch <astroelectronic at t-online.de> wrote:
>>>> I'd like to know which frames does the tmix filter use for averaging.
>>>> Let's assume tmix=frames=9.
>>>> To make the n_th frame of the output video, does it use input frames n-8
>>>> to n, or n-4 to n+4, or n to n+8?
>>>> How does the filter behave at the beginning and end of the video, where
>>>> not all required input frames exist?
>>> Filter output first frame after frames=9 it got from input. At
>>> encountering eof it simply ends.
>> I did make this test with a 5 seconds @25fps input video with
>> tmix=frames=50, so that the output should be 2 seconds shorter. But the
>> output video has the same length as the input.
> Your interpretation of test results is invalid.
> You should count frames.

Well, I did run the video in VLC and measure the duration with a 
stopwatch, and it is 5 seconds. Below is the FFprobe output.
How can I count the frames?

F:\Meteore>c:\ffmpeg\ffprobe F:\Meteore\test.mp4
ffprobe version N-93219-gc679119a73 Copyright (c) 2007-2019 the FFmpeg 
developer
s
   built with gcc 8.2.1 (GCC) 20190212
   configuration: --enable-gpl --enable-version3 --enable-sdl2 
--enable-fontconfi
g --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d 
--enable-libb
luray --enable-libfreetype --enable-libmp3lame 
--enable-libopencore-amrnb --enab
le-libopencore-amrwb --enable-libopenjpeg --enable-libopus 
--enable-libshine --e
nable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame 
--enable
-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 
--enable-libx265 -
-enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib 
--enable-gmp --enab
le-libvidstab --enable-libvorbis --enable-libvo-amrwbenc 
--enable-libmysofa --en
able-libspeex --enable-libxvid --enable-libaom --enable-libmfx 
--enable-amf --en
able-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc 
--enable-nvdec --e
nable-dxva2 --enable-avisynth --enable-libopenmpt
   libavutil      56. 26.100 / 56. 26.100
   libavcodec     58. 47.102 / 58. 47.102
   libavformat    58. 26.101 / 58. 26.101
   libavdevice    58.  6.101 / 58.  6.101
   libavfilter     7. 48.100 /  7. 48.100
   libswscale      5.  4.100 /  5.  4.100
   libswresample   3.  4.100 /  3.  4.100
   libpostproc    55.  4.100 / 55.  4.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'F:\Meteore\test.mp4':
   Metadata:
     major_brand     : isom
     minor_version   : 512
     compatible_brands: isomiso2avc1mp41
     encoder         : Lavf58.26.101
   Duration: 00:00:05.04, start: 0.000000, bitrate: 1418 kb/s
     Stream #0:0(und): Video: h264 (High 4:2:2) (avc1 / 0x31637661), 
yuv422p, 120
0x1200 [SAR 1:1 DAR 1:1], 2128 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc 
(default)

     Metadata:
       handler_name    : VideoHandler
     Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 
stereo, flt
p, 127 kb/s (default)
     Metadata:
       handler_name    : SoundHandler