Media

Why do we transcode uploaded audio files?

• To balance quality vs compression + size for the players

• To convert everything into a supported format and codec for players

• To correct the moov atom which can affect the players ability to stream the audio

What do we transcode audio files to?

• We use FFmpeg for all transcoding

• MP4 format, encoded with AAC codec (libfdk_aac)

• Bit Rate - 128Kbps (FFmpeg default)

• Sample Rate

  • We support the following sample rates - 11,025kHz, 22,050kHz, 44,100kHz, 48,000kHz
  • If an uploaded audio file doesn’t match one of those sample rates, we re-sample it to 44,100kHz

• Channels - we do not modify the channels (mono, stereo etc…). Whatever the uploaded audio file has, we respect.

Is there a file size limit for uploaded audio files?

• We apply an arbitary limit of 1Gb file size to reduce inconvenience to users. But still retain a limit to reduce issues with large transcodes (long transcodes can timeout or corrupt)
• Not all uploaded audio files are equal. A 500Mb uncompressed audio file (e.g. *.flac) can process much faster than a 100Mb highly compressed file. This can impact the time and success rate of a transcode.