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• ffmpeg : Create a fake shadow below alpha channel webm/png sequence

  6 mai 2021, par Beneos Battlemaps

  Purpose : I'd like to render out animated 3D meshes as png sequence to use them as animated tokens for virtual tabletop games. To make the mesh looks more natural I'd like to create a fake show beneath the actual token.

  


  Problem : I have a png sequence 1 (as well as a webm file created with ffmpet out of this png sequence if it makes it easier) with alpha channel. To create the webm I use :
ffmpeg -framerate 24 -f image2 -i Idle_Top.%04d.png -c:v libvpx-vp9 -crf 25 -pix_fmt yuva420p Idle_Top.webm (If its relevant). I'd like to render out the png sequence to a webm file that have the current images as well as the transparent shadow beneath the token combined.

  


  Possible workflow : I think a good way to achieve the wanted shadow effect is to use the alpha channel image as a mask on a black picture with the same resolution as the source image 2. Then you have a complete black version of the image. Then you need to place this image beneath the colored image and make a offset of 10px left and 10px down to create the ilusion of perspective 3. At the end the black image below the colored image must have a transparency as well ( 30% visibility should be enough) 4.

  


  Workflow overview

  


  Assets : I've put the webm file and the png files on my gDrive https://drive.google.com/drive/folders/1wznGaPwhKc2UyPpSZBSISa1gs3oixsHR?usp=sharing

  


  Though I work with ffmpeg on a regular basis I have no clue where to start. Can you please help me out with this interesting problem ?

  


  Best regards
Ben

  


• Generate waveforms for audio files with large amount of channels

  3 mai 2021, par motio

  I want to generate .png files displaying the waveforms of interleaved audio .wav files using the FFmpeg libraries. http://ffmpeg.org/documentation.html

  


  If the interleaved audio file contains maximum 8 channels, I manage to successfully achieve this using the following command line :

  


  ffmpeg -i 8_channels_input.wav -y -filter_complex "showwavespic=s=1920x1200:split_channels=1" -frames:v 1 8_channels_waveform_output.png


  


  However, if the interleaved audio file contains more than 8 channels, FFmpeg gives the following :

  


  


  Input #0, wav, from '30_channels_input.wav' : Duration : 00:00:02.08,
bitrate : 31752 kb/s Stream #0:0 : Audio : pcm_s24le ([1][0][0][0] /
0x0001), 44100 Hz, 30 channels, s32 (24 bit), 31752 kb/s Stream
mapping : Stream #0:0 (pcm_s24le) -> showwavespic showwavespic ->
Stream #0:0 (png) Press [q] to stop, [?] for help [auto_resampler_0 @
0x7faf5d60a3c0] Cannot select channel layout for the link between
filters auto_resampler_0 and Parsed_showwavespic_0. [auto_resampler_0
@ 0x7faf5d60a3c0] Unknown channel layouts not supported, try
specifying a channel layout using 'aformat=channel_layouts=something'.
Error reinitializing filters ! Failed to inject frame into filter
network : Invalid argument Error while processing the decoded data for
stream #0:0 Conversion failed !

  


  


  Here is the related documentation (c.f. bottom of the page) :
https://trac.ffmpeg.org/wiki/AudioChannelManipulation

  


  My problem is :
I need to generate the visual waveforms of audio files containing up to 30 channels.
All my attempts were unsuccessful so far (I am trying to define custom channel layouts and I am not sure if I am on the right track here).

  


  To simplify, I need to complete/modify the following command to make it work :

  


  ffmpeg -i 30_channels_input.wav -y -filter_complex "showwavespic=s=1920x1200:split_channels=1" -frames:v 1 30_channels_waveform_output.png 


  


  [EDIT] Remarks :

  


  I manage to generate the waveforms of a 10 channels input by combining existing layouts :

  


  ffmpeg -i 10_channels_input.wav -y -filter_complex "aformat=channel_layouts=7.1+downmix, showwavespic=s=1920x1200:split_channels=1" -frames:v 1 10_channels_waveform_output.png


  


  However, if you attempt to do it for a 30 channels input by combining 5x 6.0 layouts :

  


  ffmpeg -i 30_channels_input.wav -y -filter_complex "aformat=channel_layouts=6.0+6.0+6.0+6.0+6.0, showwavespic=s=1920x1200:split_channels=1" -frames:v 1 30_channels_waveform_output.png


  


  FFmpeg gives the following :

  


  


  [auto_resampler_0 @ 0x7ffd7002a480] [SWR @ 0x7ffd7013a000] Rematrix is
needed between 30 channels and 6.0 but there is not enough information
to do it [auto_resampler_0 @ 0x7ffd7002a480] Failed to configure
output pad on auto_resampler_0 Error reinitializing filters ! Failed to
inject frame into filter network : Invalid argument Error while
processing the decoded data for stream #0:0

  


  


  My assumption is that I need to create a custom layout using 30 unique channel IDs (c.f. https://trac.ffmpeg.org/wiki/AudioChannelManipulation bottom of the page) instead of combining existing layouts.

  


  It seems that only 25 channel IDs are available though. Creating a custom layout with 30 channels is maybe not possible at all...

  


  [EDIT 2] Remarks :

  


  I finally found the documentation I was looking for. But it still seems that generating the waveforms of 30 channels would be difficult.

  


  Here is how to create custom layouts :
https://ffmpeg.org/ffmpeg-utils.html

  


  


  A custom channel layout can be specified as a sequence of terms,
separated by ’+’ or ’|’. Each term can be :

  


  the name of a standard channel layout (e.g. ‘mono’, ‘stereo’, ‘4.0’,
‘quad’, ‘5.0’, etc.) the name of a single channel (e.g. ‘FL’, ‘FR’,
‘FC’, ‘LFE’, etc.) a number of channels, in decimal, followed by ’c’,
yielding the default channel layout for that number of channels (see
the function av_get_default_channel_layout). Note that not all channel
counts have a default layout. a number of channels, in decimal,
followed by ’C’, yielding an unknown channel layout with the specified
number of channels. Note that not all channel layout specification
strings support unknown channel layouts. a channel layout mask, in
hexadecimal starting with "0x" (see the AV_CH_* macros in
libavutil/channel_layout.h. Before libavutil version 53 the trailing
character "c" to specify a number of channels was optional, but now it
is required, while a channel layout mask can also be specified as a
decimal number (if and only if not followed by "c" or "C").

  


  See also the function av_get_channel_layout defined in
libavutil/channel_layout.h.

  


  


  e.g.

  


  Therefore, for 11 channels input :

  


  ffmpeg -i 11_channels_input.wav -y -filter_complex "aformat=channel_layouts=FL+FR+FC+BL+BR+BC+SL+SR+WL+WR+TBL, showwavespic=s=1920x1200:split_channels=1" -frames:v 1 11_waveform_output.png


  


  —> worked for me

  


  while :

  


  ffmpeg -i 11_channels_input.wav -y -filter_complex "aformat=channel_layouts=11c, showwavespic=s=1920x1200:split_channels=1" -frames:v 1 11_waveform_output.png


  


  —> does not work

  


  But :

  


  ffmpeg -i 24_channels_input.wav -y -filter_complex "aformat=channel_layouts=24c, showwavespic=s=1920x1200:split_channels=1" -frames:v 1 24_waveform_output.png


  


  —> does work

  


  and finally, what I am still trying to achieve :

  


  ffmpeg -i 30_channels_input.wav -y -filter_complex "aformat=channel_layouts=30c, showwavespic=s=1920x1200:split_channels=1" -frames:v 1 30_waveform_output.png


  


  —> does not work

  


  p.s.

  


  

  • I execute these commands in sub shells via Ruby scripts (puts %x...)

  


  • My system : macOS 10.15.6 | zsh | FFmpeg 4.4 | Ruby 2.6.3

  


  


• FFMPEG multi livestream - recorded stream send to different services like YT and Twitch at different time (on different button clicks )

  4 octobre 2022, par Ganesh

  Trying for the last 10 days and still no success, I am creating a python application that will accept the URL and visit that URL using chromium, capture that screen and send that real-time screen recording to different live stream acceptors as youtube live, twitch Twitter, Facebook live or some other sources and many of these could be multiple.

  


  There are two challenges (both challenges depend on a user action like different button clicks) -

  


  

  • The time of starting the Livestream we know only one Livestream acceptor and other acceptors could be sent via another API at any time or may not be sent on the whole live stream.

  


  • Any of the streams could be stopped at any moment including the first one which started the original live streaming service

  


  


  To Solve these challenges I am trying the following process (i took mp4 as a source for simplifying)

  


  

  • create a stream and store it into PIPE.stdout

  


  


  ffmpeg_Command_get_stream = 'ffmpeg -re -i test.mp4 -f flv pipe:1'
ffmpeg_Command_get_stream=ffmpeg_Command_get_stream.split()
pipe = sp.Popen(ffmpeg_Command_get_stream,
            stdout=sp.PIPE,
            stderr=sp.PIPE,
            bufsize=8000000,
            shell=True,
            universal_newlines=True
            )
out,err = pipe.communicate()


  


  


  • and send that stream with the help of FFMPEG to the Livestream acceptor with the click of the youtube Livestream button

    


    ffmpeg_Command_send_stream = ['ffmpeg','-i',pipe.stdout,'-f','flv',RTMPURL_YOUTUBE]

    


  


  


  Update Trying to Explain it a little more :

  


  step 1 - I need a real-time stream from the first command, so I used -re in FFMPEG

  


  step 2 - Use above stream as an input for other command and send that as an output as a Livestream to youtube (or twitch/Facebook), But the second step would happen only when the user click on the button "YT LiveStream", Here the tricky thing is there are multiple buttons (YT LiveStream, Twitch LiveStream, Facebook LiveStream) and user can click any time on any of button, also can click on all button one by one.

  


  

  


  sorry for bad explaination

  


  what I am doing wrong ? , Is this Possible ? or need to go with another process,

  


  any help would be greatly appreciated