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• FFMPEG Recording Audio from Adafruit I2S MEMS Microphone Having Issues

  24 juin 2021, par Turkey

  I am attempting to use FFMPEG to record and stream video off a Raspberry Pi Zero using the pi camera and the Adafruit I2S MEMS Microphone. I have successfully gotten video recording, but I am having trouble getting the audio correctly added on.

  


  I followed the directions at https://learn.adafruit.com/adafruit-i2s-mems-microphone-breakout/raspberry-pi-wiring-test and using their command of arecord -D dmic_sv -c2 -r 44100 -f S32_LE -t wav -V mono -v file.wav I do get a correct audio recording with no issues.

  


  However with my FFMPEG command of ffmpeg -f alsa -ar 44100 -ac 2 -c:a pcm_s32le -i default:CARD=sndrpii2scard -vcodec h264 -framerate 30 -i - -pix_fmt yuv420p -preset ultrafast -crf 0 -vcodec copy -codec:a aac -f segment -segment_time 1800 -segment_start_number 1 /RPICRecord%04d.mkv (The last bit starting at -f segment varies depending on recording vs streaming) I get audio that sorta just has a blip and then sounds like it's resetting. The actual recorded video also seems to not play correctly locally, however it does on YouTube. Testing with streaming the video and audio does the same, but it produces a consistent pattern on the audio blips. In the stream video I also finger snap 5 or so times, but you only ever hear 2, so it's for sure not recoding everything.

  


  

  • Working arecord audio

  


  • Recorded Audio Issues Example

  


  • Stream Audio Issues Example

  


  


  My limited knowledge of FFMPEG has failed me here to understand why this happens or how to debug this further to work towards a fix. Let me know if there is any additional info or logs that would be beneficial.

  


• How to apply the same FFMPEG slide transition for every slide in a sequence ?

  28 juillet 2024, par will

  I have an ffmpeg command to create an MP4 video from a sequence of N x JPEG slides. That is, I do not know how many slides there are in the sequence, it is just a directory of JPEG-s.

  


  I'd like to apply a common slide transition for every slide in the sequence. All the examples I've read seem to need to know how many slides there are before the filter is written. The idea is to use one (simple) transition/filter for every slide.

  


  So far the script looks like this :

  


      play_duration="-framerate 1/10"      #   10 seconds for testing

    ffmpeg                                          \
        ${play_duration}                            \
        -pattern_type glob                          \
        -i "./slides/*.jpg"                         \
                                                    \
         -c:v libx264                                \
         -filter_complex                             \
            "pad=ceil(iw/2)*2:ceil(ih/2)*2; fade=out:120:30"         \
                                                    \
        ./Slideshow.mp4


  


  The first filter : "pad=..." is necessary to deal with inconsistiencies in the JPEG input.

  


  My limited appreciation here is that the "fade=out:120:30" filter ought to work if I didn't need to also have the pad= construct.

  


  Example transition examples for I've come across so far — there are a great many variations on the same pattern — all look a lot like this ...

  


      ffmpeg -loop 1 -t 3 -framerate 60 -i image1.jpg -loop 1 -t 3   \
        -framerate 60 -i image2.jpg -loop 1 -t 3 -framerate 60 -i image3.jpg   \
        -filter_complex                                             \
            "[0]scale=1920:1280:force_original_aspect_ratio=decrease,pad=1920:1280:-1:-1[s0]; [1]scale=1920:1280:force_original_aspect_ratio=decrease,pad=1920:1280:-1:-1[s1]; [2]scale=1920:1280:force_original_aspect_ratio=decrease,pad=1920:1280:-1:-1[s2]; [s0][s1]xfade=transition=circleopen:duration=1:offset=2[f0]; [f0][s2]xfade=transition=circleopen:duration=1:offset=4"                 \
        -c:v libx264 -pix_fmt yuv420p                                \
        output.mp4



  


  

  • from : How to Create a Slideshow from Images using FFmpeg, as a representative example.

  


  


  The requirement is to have the same filter/transition which will apply to all slide changes. It sounded so easy at first.

  


• imgutils : add function to clear an image to black

  22 juillet 2017, par wm4

  imgutils : add function to clear an image to black
  Black isn't always just memset(ptr, 0, size). Limited YUV in particular
  
  requires relatively non-obvious values, and filling a frame with
  
  repeating 0 bytes is disallowed in some contexts. With component sizes
  
  larger than 8 or packed YUV, this can become relatively complicated. So
  
  having a generic function for this seems helpful.
  In order to handle the complex cases in a generic way without destroying
  
  performance, this code attempts to compute a black pixel, and then uses
  
  that value to clear the image data quickly by using a function like
  
  memset.
  Common cases like yuv410p10 or rgba can't be handled with a simple
  
  memset, so there is some code to fill memory with 2/4/8 byte patterns.
  
  For the remaining cases, a generic slow fallback is used.
  Signed-off-by : Anton Khirnov <anton@khirnov.net>
  Merged from Libav commit 45df7adc1d9b7.
  

  • [DH] doc/APIchanges
  • [DH] libavutil/imgutils.c
  • [DH] libavutil/imgutils.h
  • [DH] libavutil/version.h