Author Topic: HD audio still garbled  (Read 1698 times)

Post producer

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HD audio still garbled
« on: January 03, 2017, 09:02:13 PM »
Using the current app version of Avidemux on Ubuntu 14.04.1, the previously reported problem still occurs on HD recordings. Recordings made on Libreelec using TVheadend 4.1.1945. Typically, sound is normal on less commercially sensitive programme material, but as soon as a major film or drama starts the audio sounds as though the speaker is underwater. Latest example was on BBC1 HD from Crystal Palace. Still Open All Hours, audio ok, links and trailers, audio ok, Sherlock, audio garbled. If this is not digital rights management at work, then it does the same thing. Is there any hope

mean

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Re: HD audio still garbled
« Reply #1 on: January 04, 2017, 05:10:17 AM »
a sample  woulld help (10 sec is enough)
Maybe they switch codec on the fly

Post producer

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Re: HD audio still garbled
« Reply #2 on: January 11, 2017, 10:46:14 PM »
This is proving difficult since I cannot cut a clip from an existing recording as the resulting audio is incomplete. For example, vlc plays only an effects plus music track but dialog is not present although the pre avidemux version plays correctly. So I can only produce a clip by a short original recording. This involves predicting which programmes will show the problem. No luck on this so far.

Ok, track switching may be and probably is the cause, but how can it be fixed?

Jan Gruuthuse

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Re: HD audio still garbled
« Reply #3 on: January 12, 2017, 08:34:18 AM »
Can you make a 5 minute recording? Overlapping, end of standard program and start of program like Sherlock. Where the audio switch takes place.
Developers need original recording to see what is going on and probably fix this issue.
Can be fixed: switch to satellite TV.

Upload:
Use a free dropbox account, https://www.wetransfer.com/, mega or similar webservice (free public access, without registration to download your uploaded video) thank you.

Post producer

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Re: HD audio still garbled
« Reply #4 on: January 16, 2017, 09:31:13 PM »
this is the link

https://we.tl/o1V6nwPnQ6

The libreelec player shows that the audio switches from 2 tracks to 5.1 tracks just before Sherlock starts, and reproduces the audio correctly before and after the change.  Avidemux gives garbled audio after the switch and VLC plays only the effects track.

mean

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Re: HD audio still garbled
« Reply #5 on: January 17, 2017, 07:11:20 AM »
Thank you for the sample
(It's a pretty bad season :( )

Jan Gruuthuse

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Re: HD audio still garbled
« Reply #6 on: January 17, 2017, 07:17:38 AM »
VLC shows stream 1 does change from stereo to 5.1 3F2R/LFE (3 front, 2 rear and subwoofer) where the mountain rescuers are shown.

Post producer

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Re: HD audio still garbled
« Reply #7 on: January 18, 2017, 06:09:57 PM »
Here is another clip.

https://we.tl/ENuv1m2yye

Recorded at random, testing new usb tuner. This plays on Kodi video player and VLC. Audio reported as 2 track stereo by kodi. Avidemux app 99 audio garbled as before although no audio switch occurs during the recording.

Hope this gives a further clue?

Jan Gruuthuse

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Re: HD audio still garbled
« Reply #8 on: January 19, 2017, 08:03:31 AM »
confirmed:
avidemux sounds like backward
vlc plays this correctly: MPEG AAC mp4A 48000 Hz

Mediainfo:
Code: [Select]
Audio
ID                                       : 202 (0xCA)
Menu ID                                  : 17604 (0x44C4)
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Muxing mode                              : LATM
Codec ID                                 : 17
Duration                                 : 13 min 27 s
Bit rate mode                            : Variable
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 46.875 FPS (1024 spf)
Compression mode                         : Lossy
Delay relative to video                  : -872 ms
Language                                 : English

Post producer

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Re: HD audio still garbled
« Reply #9 on: January 30, 2017, 01:56:57 PM »
Is any action in progress or planned on this?

mean

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Re: HD audio still garbled
« Reply #10 on: January 31, 2017, 05:46:35 PM »
It(s in the stack of things to do
no eta

fish

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Re: HD audio still garbled
« Reply #11 on: February 03, 2017, 04:45:42 PM »
As a temporary work around, try passing the file through MKVToolNix before editing. You will probably need to  restart Avidemux and move past the first I-Frame because loading the MKV file produced by MKVToolNix  usually crashes Avidemux first time around. It's not an elegant workflow but it works for me.

Post producer

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Re: HD audio still garbled
« Reply #12 on: February 06, 2017, 06:02:11 PM »
Thanks Fish for your interest. Regret MKVtoolsNIX does not appear to fix my recordings. Do you have the fault as I described on any of your HD recordings. Are you able to fix my test samples on your system. Are you windows or Linux based?

Thanks Mean, I look forward to the fix when you can fit it in. Please let me know if I can help with any testing.

Jan Gruuthuse

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Re: HD audio still garbled
« Reply #13 on: February 06, 2017, 06:40:17 PM »
Drag & drop upon to audacity. And export  again to ac3 or other format.
On windows you need to install additional ffmeg impor/export library.
- http://www.audacityteam.org

Post producer

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Re: HD audio still garbled
« Reply #14 on: February 06, 2017, 08:50:06 PM »
Audacity offers two streams index 12e and index 132 but crashes if asked to import either. Source was my original channel 4 recording from the earlier post on this subject. There must be a better way to fix this?