ProRes file size bug and non-compliant audio

I’ve noticed a few problems exporting ProRes files, including ProRes LT.

  1. The file size is mysteriously 3-4x larger when exporting as ProRes LT. I often re-encode with the EXACT same settings in an NLE or Media Encoder to ProRes LT again! and the file size drops to 25-30% of the original? (I suspect a bug as the data rate is equivalent to ProRes 4:4:4 not LT!)

  2. Leaving the encoder audio settings on auto will often copy the original audio stream, such as AAC, AC3 etc. This is not compliant with the ProRes specification (uncompressed audio) and will cause issues when editing in another application. This needs to be fixed and forced to transcode to uncompressed audio that is compliant with the ProRes spec.

Seems to be something wirong in your encoders.json file…

Prores LT vanilla parameters should look like this:

"text": "ProRes 422 LT",
"encoder": "-c:v prores_ks -profile:v 1 -vendor apl0 -bits_per_mb 8000 -pix_fmt yuv422p10le",
"ext": [
"transcode": "aac",
"os": "windows",
"minSize": [1,1],
"maxSize": [16255,16255],
"maxBitDepth": 10,
"doNotScaleFullColorRange": "transcode"

For the audio change:
use for example pcm_s16le instead of aac under “transcode” or one of these:

alaw ->PCM A-law
f32be ->PCM 32-bit floating-point big-endian
f32le ->PCM 32-bit floating-point little-endian
f64be ->PCM 64-bit floating-point big-endian
f64le ->PCM 64-bit floating-point little-endian
mulaw ->PCM mu-law
s16be ->PCM signed 16-bit big-endian
s16le ->PCM signed 16-bit little-endian
s24be ->PCM signed 24-bit big-endian
s24le ->PCM signed 24-bit little-endian
s32be ->PCM signed 32-bit big-endian
s32le ->PCM signed 32-bit little-endian
s8 ->PCM signed 8-bit
u16be ->PCM unsigned 16-bit big-endian
u16le ->PCM unsigned 16-bit little-endian
u24be ->PCM unsigned 24-bit big-endian
u24le ->PCM unsigned 24-bit little-endian
u32be ->PCM unsigned 32-bit big-endian
u32le ->PCM unsigned 32-bit little-endian
u8 ->PCM unsigned 8-bit

and make sure to pick the transcode option instead of auto for processing.