Audio problems on some HD recordings

[rapple]

Hope this hasn't been asked before, I've had a quick look but the closest I have come is Problems with Sound on HD downloads. post-72985 - sorry not enough posts to link.

Basically on some HD files - maybe 1 in 15, 1 in 20 - I can't get audio when I play a file copied to my PC, with VLC, Media player, nor can I open it with Womble's VCR or DVD edit utility, nor can I play it via the VLC plugin in the browser. Needless to say it plays fine on the HUMAX directly. Very occasionally I get 1 that I can't open at all.

I should be clear, when I say I can't get audio, on some of the files I do get background music, but not the bulk of the sound - speech and background sounds such as footsteps, cows mooing, laughter etc.
I have a couple of series recorded, where only 1 of the files is affected. They all come from one channel in each case (not the same channel).
Using latest version of CF.

In addition to different players I tried deinstalling all codecs (as best you can on Windows) and reinstalling only VLC but nothing seemed to change.
I tried different machines and an Android tablet but the players I used showed the same.

Initially I thought that it must be something preventing the DLNA service from converting properly but then from the other thread MPC-HC was mentioned as a less fussy .ts player.
I tried installing this and I could read all the files that had so far been problematic.

Anyone any idea what might be causing this behaviour and is there something I can do to improve it. I've never had any issues with VLC before - it's been my player of choice for many years.

Thanks.

 

[Ezra Pound]

I experienced this 'background sound' only last year (Link HERE), someone on AV forums said it was due to front and rear soundtracks on DD5.1 being reversed

 

[rapple]

Interesting, that sounds closer to what I am experiencing.

I only have womble's editor here. Any recommendations for editors that can extract and manipulate audio that might be able to open these that I could try using to see if I can "clean up"/investigate the problem files?

Free ones preferred

Cheers.

 

[Black Hole]

I think what you need is a stream adjuster able to switch the properties on the individual streams within the recording, to mark the correct audio stream as "main" (or whatever). I have in the past used a tag editor to change aspect ratio on video within a stream.

Maybe there are settings already within VLC to be able to select the required audio stream.

 

[rapple]

Well, with some more experimenting, I've discovered that for those where there is no sound present I can force it in VLC by switching to the subtitle track and then back to the audio track and adjusting the snyc away from and back to 0 delay. In some I don't need to adjust the sync. I have one from a commercial station where the ad breaks are Sound OK and when it goes back to a program segment sound is lost again. Tends to suggest to me it's a combination of possible non-standard (or uncommon) data in stream and how VLC and the others handle this. Guess I need to head over to VLC forums see if they can help understand the issue before we get to trying to fix.

However it doesn't help with the ones they won't open so looks like I need to keep MPC-HC handy for viewing on PC.

Black Hole you mentioned a tag editor. Sorry, not my field, can you be more specific?

Thanks.

 

[Ezra Pound]

I think you would need something like Panhandler (link HERE) to manipulate the Dolby matrix encoding, as far as the problem not being present during the adverts, this will be due to the fact that the adverts don't carry multi-channel sound, just stereo. Another issue that is sometime encountered is the media player not being able to switch between different audio formats, accepting only the first one it encounters
EDIT
Having read the description, it looks more like Panhandler manipulates multi-channel surround sound rather than DD5.1

 

[Black Hole]

Black Hole you mentioned a tag editor. Sorry, not my field, can you be more specific?

Not off the top of my head. It does not apply to your case anyway, I was only illustrating.

I forget the exact details, but I had some digitised analogue 16:9 video which was reproducing at 4:3 - the video stream contains property tags which define the aspect ratio of the video, and these were wrong. A software package went through the video file altering all the tags to my specification, thus making the video play at 16:9.

 

[rapple]

Not off the top of my head. It does not apply to your case anyway, I was only illustrating.

I forget the exact details, but I had some digitised analogue 16:9 video which was reproducing at 4:3 - the video stream contains property tags which define the aspect ratio of the video, and these were wrong. A software package went through the video file altering all the tags to my specification, thus making the video play at 16:9.

Took a couple of days but finally managed to get an ID for the VLC forums. There is one other poster there that had a specific issue with a BBC HD file that is almost identical. There are also a couple of "similar" bugs filed. The other posters didn't appear to progress but I have asked for relevant support so that I can file a bug properly and hopefully someone will look at it. That recording came not via a Fox, which supports the theory that maybe there are some TS with the odd marker incorrectly set in the stream itself and VLC either doesn't take account of it or does so incorrectly.

Will report back if that goes anywhere.