Skip to main content ↑ ↓

Notice

Please note that most of the software linked on this forum is likely to be safe to use. If you are unsure, feel free to ask in the relevant topics, or send a private message to an administrator or moderator. To help curb the problems of false positives, or in the event that you do find actual malware, you can contribute through the article linked here.
Topic: flac and wavpack bitdepth in ffmpeg (Read 745 times) previous topic - next topic - Topic derived from FFmpeg 7.0 "Dijkstra"...
0 Members and 1 Guest are viewing this topic.

flac and wavpack bitdepth in ffmpeg

Quote from: ktf on
One of the major changes in this release is the inclusion of multithreading in the command line tool.

While I was comparing the speed of operations between the last year's and the current version of FFMPEG, I noticed an oddball behavior of the following command: ffmpeg -i in.wav out.wv. If WAV is 16-bit, then WV is 16-bit, but if WAV is 24-bit, then WV is 32-bit. Dear @Porcus, you test lossless a lot, maybe you know what's going on?


Title changed, was: [Split TOS#5 - not ffmpeg 7.0 exclusive issue] FFmpeg 7.0 "Dijkstra" released 2024-04-05
• Join our efforts to make Helix MP3 encoder great again
• Opus complexity & qAAC dependence on Apple is an aberration from Vorbis & Musepack breakthroughs
• Let's pray that D. Bryant improve WavPack hybrid, C. Helmrich update FSLAC, M. van Beurden teach FLAC to handle non-audio data

Re: flac and wavpack bitdepth in ffmpeg

Reply #1 –
Quote from: Kraeved on
If WAV is 16-bit, then WV is 16-bit, but if WAV is 24-bit, then WV is 32-bit.
ffmpeg internally knows 16-bit and 32-bit, but it doesn't have an internal representation for 24-bit. So, on decoding, it decodes to 32-bit and then 'forgets' the actual number of bits the data uses, and thus encodes to 32-bit.
Music: sounds arranged such that they construct feelings.

Re: flac and wavpack bitdepth in ffmpeg

Reply #2 –
If you know that the input is 24-bit then the option:
Code: [Select]
-bits_per_raw_sample 24
creates 24-bit WV.

Re: flac and wavpack bitdepth in ffmpeg

Reply #3 –
Ah, I thought the multithreading was for encoding audio and video separately etc., but yes decoding and encoding is a point indeed.
 

As for 24 vs 32:
* ffmpeg does that for WavPack, but not for FLAC. Precisely why I don't know, but there was no 32-bit way to do it when there was no 32-bit FLAC support. Anyway the size penalty isn't that big, since WavPack compresses away wasted bits - until you convert to something that doesn't (like, WAVE which doesn't compress neither wasted bits nor anything else)
* For 8 bits, the situation is the other way around: ffmpeg creates 8-bit WavPack, as should - but 16 bit FLAC. That is,
ffmpeg -i 8bitfile.wav outfile.flac makes a 16 bit flac file, but ffmpeg -i 8bitfile.wav outfile.wv makes an 8-bit WavPack file. (Whether source is WAVE or AIFF doesn't matter.)

Quote from: danadam on
If you know that the input is 24-bit then the option:
Code: [Select]
-bits_per_raw_sample 24
creates 24-bit WV.
But, -bits_per_raw_sample 8 does not create 8-bit FLAC.

Anyway, bloody annoying there is no way to force ffmpeg into "read input bit depth and use that for output".

Re: flac and wavpack bitdepth in ffmpeg

Reply #4 –
Quote from: Porcus
* ffmpeg does that for WavPack, but not for FLAC. Precisely why I don't know, but there was no 32-bit way to do it when there was no 32-bit FLAC support.
When ffmpeg uses 32-bit for internal processing then flac codec by itself overwrites "bits_per_raw_sample" to 24. You have to use:
Code: [Select]
-strict experimental
to stop it from doing that. With that you can produce 32-bit flacs. You can then also use:
Code: [Select]
-bits_per_raw_sample 24
yourself to overwrite it back to 24 :)

(see libavcodec/flacenc.c)

Quote from: Porcus
* For 8 bits, the situation is the other way around: ffmpeg creates 8-bit WavPack, as should - but 16 bit FLAC.
That's because wavpack codec has support for all ffmpeg internal datatypes while flac only has support for 16 and 32-bit ones.

In libavcodec/wavpackenc.c:
Code: [Select]
const FFCodec ff_wavpack_encoder = {
    ...
    .p.sample_fmts  = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_U8P,
                                                     AV_SAMPLE_FMT_S16P,
                                                     AV_SAMPLE_FMT_S32P,
                                                     AV_SAMPLE_FMT_FLTP,
                                                     AV_SAMPLE_FMT_NONE },

In libavcodec/flacenc.c:
Code: [Select]
const FFCodec ff_flac_encoder = {
    ...
    .p.sample_fmts  = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
                                                     AV_SAMPLE_FMT_S32,
                                                     AV_SAMPLE_FMT_NONE },


Merged topics, removed unnecessary reference to other topic.

Re: flac and wavpack bitdepth in ffmpeg

Reply #5 –
Yeah well, but that just pushes the question one step: why haven't they? 8-bit audio isn't exactly the latest news.