Two Tracks Get Combined To Create Distorted Audio

[noah-hornak]

Hi @ponchio thank you for this wonderful tool! I have a corrupt mp4 file that was recorded with two audio tracks in OBS. After running untrunc, I get back an mp4 with two tracks but each track is identical in audio and it seems like it combines audio from both tracks and combines them into each track to create two duplicate tracks that results in very distorted, choppy audio.

What I would expect to happen is untrunc successfully identifies both tracks through the corrupt audio and creates two codecs or tracks each with their own respectful audio as is what happens when I record with 2 microphones in OBS and my computer doesn't shut down to give me a corrupt mp4.

Here are the available stream information in audacity after importing the mp4 audio file generated by untrunc

And here are the waveforms for the audio generated by untrunc (notice the 2 tracks each with 2 mono tracks containing the same audio)

I also want to mention that I uncommented line 1333 in mp4.cpp in order to use the DOUBLEAUDIO code. When I have it commented, it generates an mp4 file twice the length of the actual recording with audio that does not play any audio in VLC and is unable to be opened in Audacity

Here is a folder containing zip files for the good audio (ok_long.mp4) and the corrupted audio (eriko.mp4):
https://drive.google.com/drive/folders/1iX7LNkdOP1Vfnn3q5a1_xQYHaFDmhvRX?usp=drive_link

Any help is greatly appreciated!

[ponchio]

Hi Noah, I have seen this issue already with OSB. I discovered that the audio packets are interleaved, but it seems different configurations are possible (I added the doubleaudio_interleaved which covers your case). Sooner or later I will manage to make some heuristic for the code to figure out this problem on his own. (Thanks for the samples!). Anyway with some simple modifications I was able to recover your audio files. You can download it here: http://pc-ponchio.isti.cnr.it/bad_fixed.mp4.gz Ciao, Federico

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On Sun, Mar 3, 2024 at 7:19 PM Noah Hornak ***@***.***> wrote: Hi @ponchio <https://github.com/ponchio> thank you for this wonderful tool! I have a corrupt mp4 file that was recorded with two audio tracks in OBS. After running untrunc, I get back an mp4 with two tracks but each track is identical in audio and it seems like it combines audio from both tracks and combines them into each track to create two duplicate tracks that results in very distorted, choppy audio. What I would expect to happen is untrunc successfully identifies both tracks through the corrupt audio and creates two codecs or tracks each with their own respectful audio as is what happens when I record with 2 microphones in OBS and my computer doesn't shut down to give me a corrupt mp4. Here are the available stream information in audacity after importing the mp4 audio file generated by untrunc Screenshot.from.2024-03-03.10-32-52.png (view on web) <https://github.com/ponchio/untrunc/assets/54489164/7eadd0f1-46df-4e44-a297-51082f3f559f> And here are the waveforms for the audio generated by untrunc (notice the 2 tracks each with 2 mono tracks containing the same audio) Screenshot.from.2024-03-03.10-57-18.png (view on web) <https://github.com/ponchio/untrunc/assets/54489164/6e66fce1-2611-40fa-8b41-19c175783c93> I also want to mention that I uncommented line 1333 in mp4.cpp in order to use the DOUBLEAUDIO code. When I have it commented, it generates an mp4 file twice the length of the actual recording with audio that does not play any audio in VLC and is unable to be opened in Audacity Here is a folder containing zip files for the good audio (ok_long.mp4) and the corrupted audio (eriko.mp4): https://drive.google.com/drive/folders/1iX7LNkdOP1Vfnn3q5a1_xQYHaFDmhvRX?usp=drive_link Any help is greatly appreciated! — Reply to this email directly, view it on GitHub <#276>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAUDV2ZI6MVHBZL37ACRJI3YWNSS5AVCNFSM6AAAAABEEEYNBWVHI2DSMVQWIX3LMV43ASLTON2WKOZSGE3DKNBYGAYTOOA> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[noah-hornak]

@ponchio Thank you so much for your help and for saving my audio! Much appreciated friend! Donation on your way!