Installation failure: av==14.4.0 fails to build from source due to missing PyPI wheels and FFmpeg 7 requirement

[Eurekaimer]

Description:
Hi openpi team,

When setting up the project using uv sync (or pip install), the installation consistently fails at the av package, which is a dependency of lerobot.

Root Cause Analysis:

1. The maintainers of the av (PyAV) library recently removed the pre-compiled wheels for version 14.4.0 from PyPI to save storage space.
2. Because no wheels are available, package managers (uv/pip) are forced to build av==14.4.0 from source.
3. Building from source explicitly requires FFmpeg 7, as stated in their build warnings.
4. However, most standard Linux distributions (e.g., Ubuntu 22.04) ship with older FFmpeg versions (e.g., FFmpeg 4) by default. This causes the C compiler to fail with errors like AVCodecParameters has no member named ch_layout.

Error Logs Snippet:

Failed to build av==14.4.0
...
Warning! You are installing from source.
It is EXPECTED that it will fail. You are REQUIRED to use ffmpeg 7.
...
error: ‘AVCodecParameters’ has no member named ‘ch_layout’; did you mean ‘channel_layout’?
error: command '/usr/bin/cc' failed with exit code 1

Workaround / Proposed Solution:
Since version 14.3.0 of av still has usable wheels available on PyPI, forcing a downgrade bypasses the source compilation entirely.

Adding the following to pyproject.toml temporarily resolves the issue:

[tool.uv]
override-dependencies = ["av==14.3.0"]

Alternatively, perhaps the dependency constraints in lerobot or openpi could be updated to av<14.4.0 until the PyAV team restores the wheels or a better FFmpeg 7 integration is provided.

Thanks for the great work on this project!

[BoxiangWang1215]

My solution is that update my server‘s FFmpeg 4 to7. After that i can build av=14.4.0 on my Ubuntu22.04 server. But i figured out other version of av still work, so is not a crucial problem, solution that you proposed is a better way to solve. BTW, Latest "lerobot"'s dependency update to av=16.x.x.

[Eurekaimer]

My solution is that update my server‘s FFmpeg 4 to7. After that i can build av=14.4.0 on my Ubuntu22.04 server. But i figured out other version of av still work, so is not a crucial problem, solution that you proposed is a better way to solve. BTW, Latest "lerobot"'s dependency update to av=16.x.x.

Thanks for sharing! Upgrading FFmpeg manually is definitely the hardcore route—respect for getting it to build. I saw the lerobot update to 16.x.x too, but it looks like this project hasn't bumped its dependency yet.

[echoes1984]

After deleting uv.lock, re-running uv sync can resolve the issue

[Eurekaimer]

After deleting uv.lock, re-running uv sync can resolve the issue

Good point! Rebuilding without uv.lock definitely works as a brute-force fix. But honestly, I feel like that's not the best route. The lock file is there for reproducibility, and deleting it risks breaking other dependencies through version drift. Just updating the specific requirement feels like a much cleaner solution.