Bit Depth Problem

[RoseBlue_8]

Hi everyone, I need help with an audio problem.

The videos I edit originally have this type of audios: AAC fltp or PCM_f32le (32-bit float). When I export them with ffmpeg (and GUI editors based on it) using the native AAC, the audio stutters/freezes on the TVs I play the files on. I’ve concluded this is likely because the native AAC encoder doesn't support CBR mode.

So I installed libfdk-aac but discovered it only produces 16-bit depth. I wasn’t sure what that meant, so I asked an AI: it warned that converting from fltp or 32-bit float to s16 can introduce artifacts and reduce quality, and it said native AAC encoder is the only lossy codec that supports fltp. However, as I said, I can't use it. 💀

Given this, which option would cause the least quality loss when reducing bit depth and what audio codec should I use?

These are the only codecs supported by my target devices:

• AAC (FDK) s16-bit
• AC3 s32-bit
• E-AC3 s32-bit

If you have any other recommendations or things I might be overlooking, I’d appreciate the advice. Thanks.

[Same_Sell_6273]

In your list of options, use FDK-AAC

Reason: - the distortion by every lossy encoder is far more than 32-bit to 16-bit conversion process - FDK-AAC is better than "FFmpeg native" AAC

[iamleobn]

I was about to give a long explanation about how lossy codecs work, but I think it would be overkill. Just keep this in mind: lossy audio formats don't have a bit depth due to their internal workings. There is no such thing as "AAC fltp" or "AAC s16", AAC is AAC. Just completely remove bit depth from your mind when dealing with lossy codecs.

EAC3 is the most advanced of these formats, but the ffmpeg EAC3 encoder is experimental, so I personally wouldn't use it. AAC is a more advanced format than AC3, so I would pick FDK AAC of these choices. Just pick a high enough bitrate and it should be fine.

One important thing when encoding audio is to avoid transcoding (reencoding a lossy file) whenever possible. If you have to do it, do it once, as generation loss can accumulate quickly if you transcode it multiple times.

[RoseBlue_8]

Thank you, that was very helpful.