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• avfilter's anull says "Rematrix is needed between stereo and 0 channels but there is not enough information to do it"

  24 mai 2017, par kuanyui

  I’m trying to write a transcoder according to FFMpeg’s official example with ffmpeg 3.2.4 (official prebuild Win32), and try to transcode a video with stereo audio stream source (from avformat’s dshow).

  In the example code, which passes anull into avfilter_graph_parse_ptr() for audio stream, and "time_base=1/44100:sample_rate=44100:sample_fmt=s16:channels=2:channel_layout=0x3" is passed into avfilter_graph_create_filter(), occurs error in the following avfilter_graph_config() :

  [auto-inserted scaler 0 @ 32f77600] w:iw h:ih flags:'bilinear' interl:0
  
  [Parsed_null_0 @ 2e9d79a0] auto-inserting filter 'auto-inserted scaler 0' between the filter 'in' and the filter 'Parsed_null_0'
  
  [swscaler @ 3331bfe0] deprecated pixel format used, make sure you did set range correctly
  
  [auto-inserted scaler 0 @ 32f77600] w:1920 h:1080 fmt:yuvj422p sar:1/1 -> w:1920 h:1080 fmt:yuv420p sar:1/1 flags:0x2
  
  [libmp3lame @ 2e90a360] Channel layout not specified
  
  [in @ 3866e8a0] tb:1/44100 samplefmt:s16 samplerate:44100 chlayout:0x3
  
  [Parsed_anull_0 @ 330e8820] auto-inserting filter 'auto-inserted resampler 0' between the filter 'in' and the filter 'Parsed_anull_0'
  
  [auto-inserted resampler 0 @ 330e8dc0] [SWR @ 3809b620] Rematrix is needed between stereo and 0 channels but there is not enough information to do it
  
  [auto-inserted resampler 0 @ 330e8dc0] Failed to configure output pad on auto-inserted resampler 0

  I’ve googled for days but didn’t find any clue for it. Doesn’t what anull do is only "Pass the audio source unchanged to the output", why libav want to resample stereo to 0 channel ? What’s going wrong ?

• Youtube-dl and Shell speed

  7 août 2016, par JJ The Second

  So I’ve been experimenting with youtube-dl on Ubuntu 14 recently and I should say downloading is well fast even I have a 1GB Ubuntu LAMP but when it comes to triggering FFMPEG and deleting process hangs for a good time. Even worked with -k but as soon as FFMPEG process is completed, it takes time to respond. I do understand this is a big subject but I’d really like to hear your thoughts, what amazes me is how a website like thisis running in less than a second ? Here is what I have,

  [youtube] UxxajLWwzqY: Downloading webpage
  
  [youtube] UxxajLWwzqY: Downloading video info webpage
  
  [youtube] UxxajLWwzqY: Extracting video information
  
  [info] Writing video description metadata as JSON to: /var/www/html/download/Icona Pop - I Love It (feat. Charli XCX) [OFFICIAL VIDEO].info.json
  
  [download] Destination: /var/www/html/download/Icona Pop - I Love It (feat. Charli XCX) [OFFICIAL VIDEO].m4a
  
  [download] 100% of 2.73MiB in 00:00
  
  [ffmpeg] Correcting container in "/var/www/html/download/title.m4a"
  
  [ffmpeg] Destination: /var/www/html/download/title.mp3
  
  Deleting original file /var/www/html/download/title.m4a (pass -k to keep)

  youtube-dl "http://www.youtube.com/watch?v=UxxajLWwzqY" --write-info-json  --extract-audio --audio-format mp3  -o "/var/www/html/download/%(title)s.%(ext)s"

  I really don’t understand how this is done so fast ? Is there anything I’m missing ?

  Thanks for your time.

• ffmpeg IP camera unable to record

  14 mai 2021, par trycatch22

  I am using an Amcrest POE camera. I have assigned it a static IP which I am able to confirm by logging into it via the browser. Its IP is 192.168.1.200.

  


  I tried following the instructions in this link but couldn't get it to work. I get :

  


  http://admin:admin@192.168.1.200/dd-a End of file


  


  The official ffmpeg documentation does not talk about -segment_time or -segment_format. What is the ffmepg command to grab a stream for a fixed duration and write it to an .mp4 file ?