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• Combining 2 FFMPEG Commands

  11 juillet 2020, par John Doe

  I'm trying to combine 2 ffmpeg commands, one which creates the video, and another which adds a simple fade to the beginning of the created video. Here's what I have :

  


  ffmpeg -y -stream_loop -1 -i "video.mp4" -stream_loop -1 -i "music.mp3" -i "audio.mp3" -filter_complex "[1:a]volume=0.1[a1];[2:a]adelay=5000|5000,apad=pad_dur=10[a2];[a1][a2]amerge=inputs=2,afade=in:st=0:d=5[audio]" -map "0:v" -map "[audio]" -c:v libx264 -c:a aac -ac 2 -ar 22050 -preset veryfast -shortest "output.mp4"

ffmpeg -y -i "output.mp4" -filter_complex "[0:v]fade=in:0:d=5" -c:a copy -preset veryfast -movflags faststart -fflags genpts "done.mp4"


  


  The two commands work perfectly fine, however the second one takes about the same amount of time to process as the first, and I feel it should be relatively easy to do the fade-in during the first encode. For my skillset atleast, I was wrong. Please could someone with more experience lend a helping hand ?

  


  Thanks.

  


• How to use FFmpeg & "tee" to UDP video (only) stream to another computer while recording to computer with USB camera

  13 juillet 2020, par pomptondrive

  I'm trying to get "tee muxer" to work with FFmpeg, but I'm not having much luck. Basically I would like to stream a USB camera with UDP to another computer with an decent/acceptable result to monitor, while recording around 15 FPS in an economical (compressed) fashion that won't take up too much disk space. Honestly, I don't understand the entire syntax of using "tee"—I guess that's obvious. I have looked at some of the FFmpeg documentation, but it doesn't seem comprehensive enough in this instance.

  


  So, currently, I have experimented a little and this works for streaming (picking up with VLC on the other computer) :

  


  ffmpeg -f v4l2 -i /dev/video0 -profile:v high -pix_fmt yuvj420p -level:v 4.1 -preset ultrafast -tune zerolatency -vcodec libx264 -r 15 -b:v 512k -s 640x480 -f mpegts -flush_packets 0 udp://192.168.0.19:5000?pkt_size=1316


  


  I've also checked and this records OK (I do NOT actually want it to ffplay on this machine ; this was just some code I found to test.) :

  


  ffmpeg -f v4l2 -i /dev/video0 -map 0 -c:v libx264 -f tee "Documents/video01.mkv|[f=nut]pipe:" | ffplay pipe:


  


  So the next objective is to combine the two with tee, and do a UDP stream to the other computer, while recording an mkv file to the computer with the camera. I've tried several ways to do this with no success ; results have been just one or the other, because my syntax is crap, or I'm just particularly inept at this particular task. ;-)

  


  After that (icing on the cake) would be to create separate *.mkv files at 15-minute intervals, and have them self-destruct after a couple of days.

  


  Any help with the tee business would be greatly appreciated.

  


• ffmpeg : adding an audio file to a video at specified delays

  15 juillet 2020, par JarsOfJam-Scheduler

  I have an array that may contain multiple occurrences of these terms : 'video, forest'. An audio file is added to the video file when the current element of this array I iterate is 'forest'. Otherwise, not. 'video and forest' elements will increment (of 5 seconds) the delay at which an audio file will be added. Example : the array contains "video, video, forest, video, forest". The first audio file will be added at delay=15000ms. The last one, at 25000ms. Computation details : 0 (initialization) + 5000 (video) + 5000 (video) + 5000 (forest) + 5000 (video) + 5000 (forest). 5000 + 5000 + 5000 = 15000. 5000*5 = 25000.

  


  I use ffmpeg to implement this program. The problem is that only one audio file is added, at the beginning of my video file. So the delays are not actually taken into account I think.

  


  Note that the video file also contains a music. The audio files that I try to add must be present in the video file in addition to this music. The first line of the following code adds the music to the video. The next lines try to add the audio files at good delays.

  


  subprocess.call(
    ['C:/Users/XYZ/Downloads/ffmpeg/bin/ffmpeg.exe', '-i', 'XYZ/my_XYZ_video.webm', '-stream_loop', '-1', '-i', 'tmp_music/original_music.wav',
     '-c:v', 'copy', '-shortest', '-fflags', '+shortest', '-max_interleave_delta', '100M',
     'XYZ/my_XYZ_video_with_music.webm']
    , cwd='C:/Users/XYZ/Desktop/XYZ/')

chosen_songs = ['video', 'forest', 'forest', 'video']

time_for_ffmpeg = 0
for chosen_song in chosen_songs:
    if chosen_song == 'video':
        print('video')
        print(time_for_ffmpeg)
        time_for_ffmpeg += 2000    

    elif chosen_song == 'forest':
        print('forest')
        print(time_for_ffmpeg)
        subprocess.call(
            ['C:/Users/XYZ/Downloads/ffmpeg/bin/ffmpeg.exe', '-i', 'XYZ/my_XYZ_video_with_music.webm', '-i', 'tmp_music/forest.mp3',
             '-filter_complex',
             '[1]adelay=' + str(time_for_ffmpeg) + '|' + str(time_for_ffmpeg) + '[a1];[0][a1]amix', '-c:v', 'copy',
             'XYZ/my_XYZ_video_with_music_with_songs.webm']
            , cwd='C:/Users/XYZ/Desktop/XYZ/')
        time_for_ffmpeg += 5000
    


  


  My question

  


  Why can't I add the audio files corresponding to the forest the specified delays (implemented by the variable time_for_ffmpeg`) ? How could I fix my code ?