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lisamelton / other_video_transcoding

Other tools to transcode videos.
MIT License
543 stars 24 forks source link

PCM mono audio passthrough? #135

Closed tylercheung closed 2 years ago

tylercheung commented 2 years ago

Hi,

This is more of a question than a bug, but I'm noticing when I'm transcoding my Criterion blu-ray rips, the older movies w/ PCM mono audio, it doesn't pass through the original audio but encodes it with libaac. Is this by design or does other_transcoding or ffmpeg doesn't recognize PCM as a pass-through-able format and gamely tries to convert it to AAC?

(also, how good is libaac now vs. the apple encoders?)

Thanks, Tyler

lisamelton commented 2 years ago

@tylercheung No, that's by design. PCM audio streams are uncompressed and often huge. In fact, they can be higher in bitrate than the transcoded video, depending on which encoder and ratecontrol method you choose. So, other-transcode, by default, will convert these streams to AAC format for mono and stereo and AC-3 for surround. It's always worked that way.

Of course, you can always add --main-audio 1=original to your options and pass PCM through directly. But I don't recommend it because that would really be missing the point of making a smaller, more portable version of your media.

I hope that answers your question.

lisamelton commented 2 years ago

BTW, libacc is terrible and no longer used by ffmpeg. Instead, ffmpeg uses a newer and better AAC encoder by default. It's not as good as the Apple encoder because, really, nothing is. But it's perfectly fine for movies. I use it all the time.

lisamelton commented 2 years ago

I'm going to assume that I answered this question and close this for now.

tylercheung commented 2 years ago

Yes - apologies for the delay in reply, but this does answer my question - thank you very much!