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

  12 juillet 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 ?

• Revision 37293 : Retour en arrière (suppression de la noisette)

  15 avril 2010, par joseph@… — Log

  Retour en arrière (suppression de la noisette)

• passing additional values to s3 event notification for lambda consumption

  8 septembre 2017, par user1790300

  I have to write code in react-native that allows a user to upload videos to amazon s3 to be transcoded for consumption by various devices. For the processing after the upload occurs ; I am reviewing two approaches :

  1) I can use Lambda with ffmpeg to handle the transcoding immediately after the uploading occurs (my fear here would be the amount of time required to transcode the videos and the effect on pricing if it takes a considerable amount of time).

  2) I can have s3 pass an sns message to a rest api after the created event occurs and the rest api generate a rabbitmq message that will be processed by worker that will perform the transcoding using ffmpeg.

  Option 1) seems to be the preferable option based on a completion time perspective. How concerned should I be with using 1) considering how long video transcoding might take as opposed to option 2) ?

  Also, regardless, I need a way to pass additional parameters to lambda or along the sns messaging that would allow me to somehow associate the user who uploaded the video with their account. Is there a way to pass additional text-based values to s3 to pass along to lambda or along sns when the upload completes, as a caveat I plan to upload the video directly to s3 using the rest layer(found this answer here : http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPUT.html#RESTObjectPUT-responses-examples) ?