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• Parsing custom track data from ARCore mp4 recordings

  11 July 2022, by George Ellickson

  I'm using the Android ARCore Recording API to record custom data per frame and replay those values in tests to instrument test our ARCore functionality on devices and in CI. However, separately I'd also like to parse the generated mp4 recordings myself, outside of ARCore, and use my per frame recorded data for analysis. In my ARCore app, I'd like to simply be able to add custom text data like following, encoded as utf-8 strings (or really any other simple encoding) for the given ARCore frame:

  


  val data = "Hello world!"
val buffer = ByteBuffer.wrap(data.encodeToByteArray())
frame.recordTrackData(TRACK_UUID_MY_DATA, buffer


  


  I can't find any docs or good examples though of parsing the mp4 from ARCore and no luck in their arcore-android-sdk repo either. I've tried ffmpeg / ffprobe to figure out how the data is bundled into the MP4, but I'm stumped on which track to use and how best to deserialize as I'm unsure how the bytes are actually encoded under the hood.

  


  Using ffmpeg, I just get information like this about the tracks:

  


  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'HoverCapture/ar-recording-tests/src/androidTest/res/raw/ar_recording_2_photos.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2022-01-20T22:03:13.000000Z
  Duration: 00:00:17.12, start: 0.000000, bitrate: 26865 kb/s
  Stream #0:0[0x1](und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p(tv, unknown/bt470bg/unknown, progressive), 1920x1080, 25615 kb/s, 28.08 fps, 29.58 tbr, 90k tbn (default)
    Metadata:
      creation_time   : 2022-01-20T22:03:13.000000Z
      handler_name    : ISO Media file produced by Google Inc. Created on: 01/20/2022.
      vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](und): Data: none (mett / 0x7474656D), 18 kb/s (default)
    Metadata:
      creation_time   : 2022-01-20T22:03:13.000000Z
      handler_name    : ISO Media file produced by Google Inc. Created on: 01/20/2022.
  Stream #0:2[0x3](und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p(tv, unknown/bt470bg/unknown, progressive), 640x480, 1929 kb/s, 28.12 fps, 29.42 tbr, 90k tbn (default)
    Metadata:
      creation_time   : 2022-01-20T22:03:13.000000Z
      handler_name    : ISO Media file produced by Google Inc. Created on: 01/20/2022.
      vendor_id       : [0][0][0][0]
  Stream #0:3[0x4](und): Data: none (mett / 0x7474656D), 18 kb/s (default)
    Metadata:
      creation_time   : 2022-01-20T22:03:13.000000Z
      handler_name    : ISO Media file produced by Google Inc. Created on: 01/20/2022.
  Stream #0:4[0x5](und): Data: none (mett / 0x7474656D), 54 kb/s (default)
    Metadata:
      creation_time   : 2022-01-20T22:03:13.000000Z
      handler_name    : ISO Media file produced by Google Inc. Created on: 01/20/2022.
  Stream #0:5[0x6](und): Data: none (mett / 0x7474656D), 54 kb/s (default)
    Metadata:
      creation_time   : 2022-01-20T22:03:13.000000Z
      handler_name    : ISO Media file produced by Google Inc. Created on: 01/20/2022.
  Stream #0:6[0x7](und): Data: none (mett / 0x7474656D), 0 kb/s (default)
    Metadata:
      creation_time   : 2022-01-20T22:03:13.000000Z
      handler_name    : ISO Media file produced by Google Inc. Created on: 01/20/2022.
  Stream #0:7[0x8](und): Data: none (mett / 0x7474656D), 6 kb/s (default)
    Metadata:
      creation_time   : 2022-01-20T22:03:13.000000Z
      handler_name    : ISO Media file produced by Google Inc. Created on: 01/20/2022.


  


• FFMPEG:Invalid buffer size when converting video

  30 July 2022, by Sar sinua

  I'm trying to Pipe bytes in to FFMPEG in python and I've faced a problem.

  


  import subprocess
from io import BytesIO

with open('input.mp4', 'rb') as f:
    input_byte=f.read()
command='ffmpeg -y -f rawvideo -video_size 320x240 -pixel_format yuv420p -framerate 15 -i pipe:0 -codec:a copy out.mp4'
process = subprocess.Popen(command, stdin=subprocess.PIPE, shell=True)

process.stdin.write(input_byte)
process.stdin.close()


  


  The error I get is Invalid buffer size, packet size 63420 < expected frame_size 115200 Error while decoding stream #0:0: Invalid argument

  


  You can download the video from here.

  


  ffmpeg version 2022-05-12-git-30e2bb0f64-full_build-www.gyan.dev

  


• Why A .FLAC File Converted by FFMPEG Cause File Explorer Unresponse on Windows 10 [closed]

  20 July 2022, by Alex King

  My File Explorer Always showing "Working on it."
I've tried many resolutions.
First,I disconnect my NAS drive. seems fine.
I test many times on diffirient windows 10/11 versions.
I thought it was SMB problem on windows. But i was wrong.

  


  Today I'm using FFMPEG convert .wav to .flac.

  


  .\ffmpeg.exe -i $Source -c:a flac $Dest 


  


  Just simple like this. Blow my computer up.

  


  Even worse, explorer.exe crash after I'm trying to open FF output folder.

  


  It's not the poblem from "Quick access" or "Search Index".

  


  I'm now 100% percent confirm the flac files that ffmpeg made will cause file explorer crash.

  


  I can't solve it without knowing the reason.

  


  Might related to audio file tag vorbis?

  


  This is my FFMPEG info

  


  ffmpeg version n5.0.1-4-ga5ebb3d25e-20220428 Copyright (c) 2000-2022 the FFmpeg developers

built with gcc 11.2.0 (crosstool-NG 1.24.0.533_681aaef)