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• Transition between FFMpeg streams

  25 juillet 2021, par spectacularbob

  I have been running a Youtube livestream for a while and I am developing a solution so that I can run the stream remotely through a browser. My plan is to have an ASP.net core web api project running a background service that when I send the streaming information to it, it launches FFMpeg to stream a USB webcam. I also need to be able to press a button to "mute" the stream so it shows a blank video with some text overlay (i.e. "Technical Difficulties").

  


  My solution so far is to use two instances of FFMpeg. When I switch modes, I kill one process and start the other one. I have gotten it working somewhat, but when I switch back and forth between "mute mode" and "streaming mode", Youtube seems to choke on the stream being changed. I suspect it's because when I go from mute mode back to stream mode, youtube doesn't recognize that the mute mode has ended. Also, mute mode displays the text like I want, but it causes the Youtube player to stop being "live" so that if I do get the regular stream going again, the user has to click the "Live" button to be up to date.

  


  Here's the command line for both modes :

  


  Stream Mode :

  


  ffmpeg.exe -f dshow -i video="<webcam>" -f dshow -i audio="<microphone>" -vcodec libx264 -pix_fmt yuv420p -preset veryfast -r 30 -g 60 -b:v 3500k -f flv rtmp://a.rtmp.youtube.com/live2/<stream key="key">&#xA;</stream></microphone></webcam>

  


  Mute Mode (blank.mp4 is a 3 second long blank video) :

  


  ffmpeg.exe -stream_loop -1 -i ./FFMpeg/blankvid.mp4 -vf "drawtext=fontfile=C\\\\:/Windows/Fonts/Arial.ttf:text=&#x27;Technical Difficulties&#x27;:fontcolor=white:fontsize=60:box=1:boxcolor=black@0.5:boxborderw=5:x=(w-text_w)/2:y=(h-text_h)/2" -vcodec libx264 -pix_fmt yuv420p -preset veryfast -r 30 -g 60 -b:v 3500k -f flv -flvflags no_duration_filesize rtmp://a.rtmp.youtube.com/live2/<stream key="key">&#xA;</stream>

  


  Last note : I know that there may be a way using a color filter to create the black video, rather than having a blankvid.mp4. If you also know how to get the parameters for that, it would be very helpful.

  


• Adding album cover art to FLAC audio files using `ffmpeg`

  27 décembre 2022, par user5395338

  I have ripped files from an audio CD I just bought. I ripped using the Music app on my Macbook Pro, Catalina 10.15.6 - output format was .wav as there was no option for FLAC. My plan was to change format using ffmpeg :

  


  % ffmpeg -v
ffmpeg version 4.4 Copyright (c) 2000-2021 the FFmpeg developers


  


  Except for the "album cover artwork" addition, the .wav-to-.flac conversion implemented in the short bash script below seems to have worked as expected :

  


  #!/bin/bash
for file in *.wav
do
echo $file 
ffmpeg -loglevel quiet -i "$file" -ar 48000 -c:a flac -disposition:v AnotherLand.png -vsync 0 -c:v png "${file/%.wav/.flac}"
done


  


  A script very similar to this one worked some time ago on a series of FLAC-to-FLAC conversions I had to do to reduce the bit depth. However, in that case, the original FLAC files already had the artwork embedded. Since this script produced usable audio files, I decided that I would try adding the artwork with a second ffmpeg command.

  


  I did some research, which informed me that there have been issues with ffmpeg (1, 2, 3, 4) on adding album artwork to FLAC files.

  


  I have tried several commands given in the references above, but still have not found a way to add album artwork to my FLAC files. The following command was a highly upvoted answer, which I felt would work, but didn't :

  


  % ffmpeg -i "01 Grave Walker.flac" -i ./AnotherLand.png -map 0:0 -map 1:0 -codec copy -id3v2_version 3 -metadata:s:v title="Album cover" -metadata:s:v comment="Cover (front)" output.flac

...


Input #0, flac, from '01 Grave Walker.flac':
  Metadata:
    encoder         : Lavf58.76.100
  Duration: 00:06:59.93, start: 0.000000, bitrate: 746 kb/s
  Stream #0:0: Audio: flac, 48000 Hz, stereo, s16
Input #1, png_pipe, from './AnotherLand.png':
  Duration: N/A, bitrate: N/A
  Stream #1:0: Video: png, rgba(pc), 522x522, 25 fps, 25 tbr, 25 tbn, 25 tbc
File 'output.flac' already exists. Overwrite? [y/N] y
[flac @ 0x7fb4d701e800] Video stream #1 is not an attached picture. Ignoring
Output #0, flac, to 'output.flac':
  Metadata:
    encoder         : Lavf58.76.100
  Stream #0:0: Audio: flac, 48000 Hz, stereo, s16
  Stream #0:1: Video: png, rgba(pc), 522x522, q=2-31, 25 fps, 25 tbr, 25 tbn, 25 tbc
    Metadata:
      title           : Album cover
      comment         : Cover (front)
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #1:0 -> #0:1 (copy)

...



  


  I don't understand the error message : Video stream #1 is not an attached picture. It seems to imply that that the artwork is "attached" (embedded ???) in the input file, but as I've specified the artwork is a separate file, this makes no sense to me.

  


• FFMPEG/NVDEC Fails When Under 7 Frames

  13 août 2021, par Meme Machine

  I was looking the examples from NVIDIA's repository, specifically their Encoding and Decoding projects. I downloaded the desktop duplication project, which allows you to capture a certain number of frames from the desktop as raw h264. I also got AppDecode, which decodes and displays frames from an input file. I noticed that if I try and capture only a single frame, it fails to decode the input file.

  


  Here is the output

  


  C:\Users\Admin>C:\Users\Admin\source\repos\video-sdk-samples\Samples\x64.Debug\AppDecD3d -d3d 11 -i C:\Users\Admin\source\repos\video-sdk-samples\nvEncDXGIOutputDuplicationSample\x64\Debug\ddatest_0.h264
GPU in use: NVIDIA GeForce RTX 2080 Super with Max-Q Design
Display with D3D11.
[INFO ][17:59:47] Media format: raw H.264 video (h264)
Session Initialization Time: 39 ms
[INFO ][17:59:47] Video Input Information
        Codec        : AVC/H.264
        Frame rate   : 30000/1000 = 30 fps
        Sequence     : Progressive
        Coded size   : [1920, 1088]
        Display area : [0, 0, 1920, 1080]
        Chroma       : YUV 420
        Bit depth    : 8
Video Decoding Params:
        Num Surfaces : 20
        Crop         : [0, 0, 0, 0]
        Resize       : 1920x1088
        Deinterlace  : Weave

Total frame decoded: 7
Session Deinitialization Time: 10 ms

C:\Users\Admin>C:\Users\Admin\source\repos\video-sdk-samples\Samples\x64.Debug\AppDecD3d -d3d 11 -i C:\Users\Admin\source\repos\video-sdk-samples\nvEncDXGIOutputDuplicationSample\x64\Debug\ddatest_0.h264
GPU in use: NVIDIA GeForce RTX 2080 Super with Max-Q Design
Display with D3D11.
[INFO ][17:59:54] Media format: raw H.264 video (h264)
[h264 @ 0000023B8AB5C3A0] decoding for stream 0 failed
Session Initialization Time: 42 ms
[INFO ][17:59:54] Video Input Information
        Codec        : AVC/H.264
        Frame rate   : 30000/1000 = 30 fps
        Sequence     : Progressive
        Coded size   : [1920, 1088]
        Display area : [0, 0, 1920, 1080]
        Chroma       : YUV 420
        Bit depth    : 8
Video Decoding Params:
        Num Surfaces : 20
        Crop         : [0, 0, 0, 0]
        Resize       : 1920x1088
        Deinterlace  : Weave

Total frame decoded: 6
Session Deinitialization Time: 10 ms


  


  I started from 10 frames and counted down to 6 where it eventually failed. It is important for me to know why this happens, because I plan to implement this decoder into my project, and will be feeding it single frames from a stream.

  


  Oh, and also I noticed the coded size is 1088 by 1920 instead of 1080 according to the output log. Not sure why that is occurring or if it is relevant