LibVLC UWP v3.3.2 has audio issue

Hi @huynhsontung,

Thanks for the report. I believe you, but my ears can't hear the difference. Please share all verbose logs. Do you reproduce with any audio file?

Hi @mfkl,

Audio file for comparison: https://www.transfernow.net/dl/20231119ZtKpl1Vi

The snippet in the video is from 5:00 to 5:08.

The following log is from me open the file and seek to 5:00, let it play to 5:08 then pause.

On v3.3.2 with this issue:

11192023 110126 PM - LibVLC.log

On v3.3.1 without this issue:

11192023 111308 PM - LibVLC.log

Thanks. The additional emulated startcode look like it could be a clue.

I've looked at the release notes of most 3.x release and can't find anything related to mpegaudio or audio on windows that could be linked to this. Neither in the VLC audio output for UWP, though it's probably UWP specific.

The next step would be making a 3.x UWP build with the latest 3.x libvlc source code and see if the issue is still present. If it is not, push that to nuget. If the error is still present, then it's a bug, and we need to pinpoint the commit that introduced the problem (somewhere between 3.0.12 and 3.0.16 apparently).

I've made a build you can access here https://1drv.ms/u/s!AlM7XlDZl-1y02XxPrLwaCVNYEgQ?e=sjJYnF

Or, if you don't have time to test, please share the test file again (I've saved it on another computer that I don't have access to at the moment).

You forgot to include the winrt access module so I couldn't open any StorageFile in a UWP app.

I forked your repo and built my own nupkg here huynhsontung/libvlc-nuget@106c0c1

Unfortunately, the issue persists with libvlc 3.0.20

1212023 122720 AM - LibVLC.log

The audio used for testing: Chopin - Ballade No. 1 in G minor Op. 23(MP3_160K).mp3

Thanks, I committed some of your fixes back to the repo.

So the next step will be to test 3.0.13, 3.0.14, 3.0.15 and 3.0.16 to find out in which release this regression was introduced. This will make it easy for core devs to find and fix the offending commit.

but my ears can't hear the difference

Ok upon listening with my headset, I can clearly hear the crackling noise. Nothing in the logs though, that's weird.

Now I can't reproduce, with 3.0.20 (no access module built, just playing the chopin song from HTTP). https://1drv.ms/u/s!AlM7XlDZl-1y03Q9soOUNKUECi92?e=XxUNBu. Built 3.0.13, 3.0.14, 3.0.15 also couldn't repro (build without https://code.videolan.org/videolan/libvlc-nuget/-/tree/master/patches?ref_type=heads).

vlc!4656 (closed)

@huynhsontung can you please try the following with the latest nuget libvlc build (3.3.2):

LibVLC = new LibVLC(enableDebugLogs: true, eventArgs.SwapChainOptions.Concat(new string[] { "--audio-resampler=speex_resampler" }).ToArray());

Seems to fix it here. If you confirm, I'll make it default in the next libvlcsharp release.

I can confirm this resolves the audio crackling issue. Unfortunately, a new issue arises. The audio is now stuttering! I can reliably trigger this by seeking around the audio file.

output.mp4

Can you reproduce without the debugger attached?

Good call. I couldn't reproduce when built in release mode and without the debugger attached. I think it is good to go.

Will be fixed by https://github.com/videolan/libvlcsharp/pull/349

closed

Many of my users have reported the stuttering audio problem after upgrading LibVlcSharp from 3.7.0 to 3.9.0

Audio stuttering bug · Issue #427 · huynhsontung/Screenbox (github.com)

Some observations:

This problem occurs depending on the machine or file type.
Stuttering may not happen at the start of the playback but can be triggered when quickly seeking through the file.
Pausing and then continuing does not fix the stuttering.
Changing the playback speed can sometimes resolve the issue.

LibVLC UWP v3.3.2 has audio issue

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