Speex decoding speed regression?

[Ronald]

Summary of the bug:
ffplay plays .spx very slowly
How to reproduce:

% ffplay test.spx
built on arch linux
ffplay version n7.0.1 Copyright (c) 2003-2024 the FFmpeg developers
built with gcc 14.1.1 (GCC) 20240522
configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-amf --enable-avisynth --enable-cuda-llvm --enable-lto --enable-fontconfig --enable-frei0r --enable-gmp --enable-gpl --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libdav1d --enable-libdrm --enable-libdvdnav --enable-libdvdread --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libharfbuzz --enable-libiec61883 --enable-libjack --enable-libjxl --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libplacebo --enable-libpulse --enable-librav1e --enable-librsvg --enable-librubberband --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpl --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxml2 --enable-libxvid --enable-libzimg --enable-mbedtls --enable-nvdec --enable-nvenc --enable-opencl --enable-opengl --enable-shared --enable-vapoursynth --enable-version3 --enable-vulkan
libavutil      59.  8.100 / 59.  8.100
libavcodec     61.  3.100 / 61.  3.100
libavformat    61.  1.100 / 61.  1.100
libavdevice    61.  1.100 / 61.  1.100
libavfilter    10.  1.100 / 10.  1.100
libswscale      8.  1.100 /  8.  1.100
libswresample   5.  1.100 /  5.  1.100
libpostproc    58.  1.100 / 58.  1.100

[Ronald]

It plays the pronunciation for "hello".

[Ronald]

In an old version (about one or two weeks ago) of ffplay, it plays .spx correctly.
vlc plays .spx correctly.
A sample .spx file is in attachment.

[MasterQuestionable]

͏    Speex appears to be a much defunct codec. ("obsoleted by Opus")

͏    Please help ascertain the exact regression window, if you deem it important.
͏    (simple revert may be applicable..?)

[Ronald]

If defunct, removing it is better than making it buggy.

[MasterQuestionable]

͏    Half-broken better than completely-broken for this case. Supposedly.
͏    Haven't analyzed in detail, but it seems to affect realtime playback (not transcoding)?

[shenlebantongying]

Cannot we just delete the native speex codec?

FFmpeg currently has 2 speex decoder.

 A....D speex                Speex
 A....D libspeex             libspeex Speex (codec speex)

The native one (speex) has been broken since the release of 7.0. Either nobody really cares or it doesn't worth the time and no one is motivated to fix it.

Having a working one is better than having a broken one. The libspeex one simply works.

[shenlebantongying]

The exact error is in libavcodec/speexdec.c -> parse_speex_extradata where the frame_size calculation is wrong.

[MasterQuestionable]

͏    Would you propose the fix directly? (GitHub direct commit)
͏    Alike: ​https://trac.ffmpeg.org/ticket/5514#comment:22

͏    Meanwhile "-c:a libspeex" (as input option (before ͏"-i") ) should workaround.


͏    Known that there are several other buggy codecs too.
͏    "aac", "opus", "vorbis", ...
͏    Maybe the better fix is to change the default decoder?

[shenlebantongying]

Hi, I made a patch by poking around last night.

https://ffmpeg.org/pipermail/ffmpeg-devel/2025-January/338959.html

I am not sure about correctness because I have almost no relevant knowledge.

However, it does fix the test files in the bug reports. Someone more competent maybe can take a look and take over to do it properly.

Maybe the better fix is to change the default decoder?

This seems more realistic.

[James]

Should be fixed in 4a0e1cfc6f33d152e007849f6de7028d651de2af

[shenlebantongying]

Thank you, James! I tested locally, it works :)

However, at the exact same location and also frame_size related, there are other test files that don't work in another ticket #11054.

I put a code change in #11054 that only works on the specific test files.