Use latest version of FLAC inside Docker image

[rodfeli]

I don't know if the flac used to make the downsample is hard coded or not, but I see that it uses version 1.3.3 while on my computer I have version 1.5.0.

$ flac --version
flac 1.5.0

$ metaflac --version
metaflac 1.5.0

In case it is included in the tool, can it be updated in the next compilation?

Thanks!!

[RogueOneEcho]

Are you using the caesura via docker?

If so the version of flac is what is built into the container hence why it differs to your computer.

The dependencies are sourced from the Alpine packages which does look to be running an older version: https://pkgs.alpinelinux.org/package/edge/main/x86_64/flac

I'm not sure if there are any benefits of using the latest versions, typically package managers stick with stable versions rather than being cutting edge. I'll have a look in to this.

[RogueOneEcho]

Disclosure: An AI tool was used to investigate the changes however I've manually checked each source and it seems accurate enough to conclude that updating to newer versions is worthwhile.

Version Comparison

Tool	Alpine v3.21	Release Date	Latest Upstream	Release Date	Gap
FLAC	1.4.3	Jun 2023	1.5.0	Feb 2025	Significant
LAME	3.100	Oct 2017	3.100.1	Sep 2020	Minimal
SoX	14.4.2	Feb 2015	14.4.2	Feb 2015	None

FLAC 1.5.0 - Strong case for update

Key improvements in FLAC 1.5.0:

• Multithreaded encoding - Major performance improvement for transcoding
• flac -t now warns about ID3v1 metadata and frame number issues
• MD5 sum verification when re-encoding FLAC from FLAC
• Symlink detection when modifying metadata (security improvement)

libFLAC version 14

The bump from libFLAC 12/13 to 14 is due to API additions, not breaking changes. Existing code should work after rebuilding. The porting guide describes minor ABI changes with no obvious API breaks requiring source patches.

New API additions include:

• Extended metadata interface functions for Ogg FLAC
• Enhanced callback behavior for Ogg FLAC encoding
• Writing to new file when changing metadata (vs overwriting in place)

LAME 3.100 - No urgent need

LAME 3.100 is essentially current. The 3.100.1 patch (Sep 2020) had no encoding library changes. Core development slowed since 2024. A quality regression patch (Ticket #516) remains unofficially merged. Alpine's version is fine.

SoX 14.4.2 - No updates available

SoX 14.4.2 is the latest upstream (Feb 2015). Development appears stalled but the tool remains functional and widely used.

Recommendation

FLAC 1.5.0's multithreading could meaningfully improve transcode performance. Options:

1. Wait for Alpine - They'll eventually package 1.5.0
2. Build FLAC from source in Dockerfile - More complexity but immediate benefit
3. Use Alpine edge - May have newer packages but less stable base

Sources

• FLAC 1.5.0 Release
• FLAC Changelog
• FLAC GitHub Releases
• LAME SourceForge
• SoX SourceForge
• Alpine Packages

[RogueOneEcho]

Work is now complete but it needs checking before being merged into main and released:
https://github.com/RogueOneEcho/caesura/tree/build-flac-from-source

[RogueOneEcho]

Completed in 9752fb2

[rodfeli]

Hello,
I'm testing the latest version to check the functionality of FLAC 1.5 and I've found that it's still using version 1.3.3. Am I doing something wrong? I have FLAC 1.5 in my seedbox, but I understand that FLAC 1.5 is also integrated into Docker? I don't understand why it's using 1.3.3...

Look:

This is what I get when I run:

caesura --version
caesura 0.27.1 caesura/0.27.1 (release)
flac 1.5.0 flac 1.5.0
lame 3.100 LAME 64bits version 3.100 (http://lame.sf.net)
sox 14.4.2 sox: SoX v14.4.2

And this is the test I made:

Source (Flac 24):

Transcode (Flac 16):

Thanks for the help!

[RogueOneEcho]

I'm unable to view those images. Can you attach to github directly

[rodfeli]

I'm unable to view those images. Can you attach to github directly

Done (in original msg)

p.s.: I am using this release: [caesura-0.27.1-x86_64-unknown-linux-musl.tar.xz] on a Debian GNU/Linux 11 (bullseye)

Thanks!

[RogueOneEcho]

tl;dr

SoX uses its own version of FLAC.

sox (14.4.2+git20190427-2+deb11u2 -> libsox-fmt-base (14.4.2+git20190427-2+deb11u2) -> libflac8 (1.3.3-2+deb11u2)

---

The FLAC version shown in the transcoded files comes from SoX, not the flac binary.

When caesura transcodes a 24-bit FLAC source to 16-bit FLAC, it uses SoX to handle the resampling and encoding - the flac binary isn't involved.

You can see that in the transcode job factory where FLAC targets use Variant::Resample, and the resample command which builds the SoX command.

SoX has its own built-in FLAC encoder (libFLAC), and on your system that's version 1.3.3 - regardless of which flac binary you have installed separately. The flac 1.5.0 binary is only used when transcoding to MP3 (for decoding).

The output files are perfectly valid - this is just a cosmetic difference in the metadata. To get 1.5.0 in the FLAC output you'd need a version of SoX built against the newer libFLAC.

If you're really keen on using the latest version you could try installing a newer version of SoX (or sox_ng) that is built against flac 1.5.0.

I already went down this rabbit hole myself and it gets complicated. I ended up setting up a GitHub Actions pipeline to build FLAC and SoX_ng from source and distribute the binaries.

You can see details on how to use them here, however be aware these are untested and I have no idea how reliable they will be:

https://github.com/RogueOneEcho/caesura/blob/main/docs/DEPENDENCIES.md#install-prebuilt-sox_ng-binaries