[FFmpeg-user] Question about tmix filter

[Paul B Mahol]

On 3/6/19, Paul B Mahol <onemda at gmail.com> wrote:
> On 3/6/19, Michael Koch <astroelectronic at t-online.de> wrote:
>> 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?
>
> Old fashioned way - by hand.

-f null -

AKA null muxer counts frames for you.


>
>>
>> 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
>>
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>