lavcac3enc filter broken with ffmpeg 8.0.x - "unsupported conversion: spdif-ac3 -> floatp

mpv Information

Other Information

- Linux version:
- Kernel Version:
- GPU Model:
- Mesa/GPU Driver Version:
- Window Manager and Version:
- Source of mpv:
- Latest known working version:
- Issue started after the following happened:

Reproduction Steps

System

• OS: openSUSE Tumbleweed-Slowroll
• mpv: 0.41.0+git20260309.07c3ff3725 (from openSUSE repo)
• ffmpeg: 8.0.1 (libavcodec62, libswresample6) from Packman
• PipeWire: 1.5.85 and 1.6.1 (both tested, same result)
• GPU: NVIDIA RTX 2070 SUPER
• Audio: HDMI extractor (HDP-V104) via PipeWire sink alsa_output.pci-0000_09_00.1.hdmi-stereo-extra2

Problem

The lavcac3enc audio filter stopped working after upgrading ffmpeg to 8.0.1.

Error

Failed to parse codec profile.
[swresample] unsupported conversion: spdif-ac3 -> floatp
[swresample] libswresample failed to initialize.
Disabling filter lavcac3enc.00 because it has failed.
AO: [pipewire] 48000Hz stereo 2ch spdif-ac3
[ao/pipewire] Stream in error state, trying to reload...
[ao/pipewire] Error during playback: No such file or directory, no target node available

Reproduction

mpv --no-config
--audio-device=pipewire/alsa_output.pci-0000_09_00.1.hdmi-stereo-extra2
--audio-spdif=ac3,dts
--af=lavcac3enc
file.mkv

Workaround

Using ALSA directly (without PipeWire) works:
mpv --no-config
--ao=alsa
--audio-device=alsa/hdmi:CARD=NVidia,DEV=2
--audio-spdif=ac3,dts
file.mkv

But this requires stopping PipeWire which breaks the desktop environment.

Notes

• Works with ffmpeg 7.1.3 (libavcodec61)
• Broken with ffmpeg 8.0.1 (libavcodec62)
• The filter lavcac3enc exists in mpv --af=help output
• PipeWire sink reports formats: ac3-iec61937, dts-iec61937 (not spdif-ac3)
• mpv attempts spdif-ac3 format which PipeWire 1.6.x no longer accepts

Expected Behavior

AC3 bitstream passthrough via lavcac3enc to HDMI extractor (working with ffmpeg 7.x).

Actual Behavior

Failed to parse codec profile.
[swresample] unsupported conversion: spdif-ac3 -> floatp
[swresample] libswresample failed to initialize.
Disabling filter lavcac3enc.00 because it has failed.
AO: [pipewire] 48000Hz stereo 2ch spdif-ac3
[ao/pipewire] Stream in error state, trying to reload...
[ao/pipewire] Error during playback: No such file or directory, no target node available

Log File

xxx

Sample Files

No response

I carefully read all instruction and confirm that I did the following:

• I tested and confirmed that the issue exists with the latest release version or newer.
• I provided all required information including system and mpv version.
• I produced the log file with the exact same set of files, parameters, and conditions used in "Reproduction Steps", with the addition of --log-file=output.txt.
• I produced the log file while the behaviors described in "Actual Behavior" were actively observed.
• I attached the full, untruncated log file.
• I attached the backtrace in the case of a crash.

Begin at mpv's lavcac3enc audio-filter entry point and the PipeWire audio-output path, using the supplied reproduction command and comparing ffmpeg 7.1.3 with 8.0.1. Done means AC3 passthrough reaches the HDMI extractor through PipeWire without the unsupported conversion, filter initialization, or stream errors.