[vlc-devel] Re: your vlc audio patch

[Jean-Alexis Montignies]

Yes there is a "bug" (in fact more a non implemented yet feature) in 
the AC3 filter in VLC.
For testing your set up, you can use the .vob file at 
http://www.matroxusers.com/Reviews/SoftwareDVD/AC3TEST.zip

You'll see that by default, the channel order is set for a one rear, 
one center, left and right setup. It looks like the channel order for 5 
channel includes LFE but only one rear channel.

My patch I didn't release because it doesn't fix the problem, just hide 
it in my particular case. It's not hard to fix, but I did not have the 
time yet.
This is all in vlc/modules/audio_filter/converter/a52tofloat32.c

Index: a52tofloat32.c
===================================================================
--- a52tofloat32.c      (revision 7893)
+++ a52tofloat32.c      (working copy)
@@ -247,7 +247,7 @@
      { 0, 0, 0, 0, 0, 0 },       /* 1 ch */
      { 0, 1, 0, 0, 0, 0 },       /* 2 */
      { 1, 2, 0, 0, 0, 0 },       /* 3 */
-    { 1, 3, 2, 0, 0, 0 },       /* 4 */
+    { 0, 1, 2, 3, 0, 0 },       /* 4 */
      { 1, 3, 4, 2, 0, 0 },       /* 5 */
      { 1, 3, 4, 5, 2, 0 }};      /* 6 */

Good WWDC :)

Jean-Alexis Montignies
http://www.sente.ch/

On 24 juin 04, at 15:58, Mark Wells wrote:

> Matt,
>
> Thanks for your reply, it helps to explain my situation pretty well. 
> So if I isolate a specific audio format (eg 6-channel) by 
> commenting-out all the other support (except mono) then the AC3 stream 
> plays perfectly. I *think* that once specific format selection works 
> (ie once the menus successfully allow you to change between stereo, 
> 5.1, 7.1 etc) then this problem will disappear.
>
> To answer your question, I'm testing using one of our own devices, the 
> OXFW970 (http://www.oxsemi.com/press/jan04/index2.html).
>
> An update so far, for anyone interested.....
>
> I notice that in ChannelsToAoutVar there is a 5-channel support option 
> (3 Front 2 Rear) however there is no initial 5 channel PCM support 
> available to complement this! So I have added this, and opened the 
> correct physical channels. The channel allocation seems to be all 
> wrong tho, as main audio comes out of channel 1 (front left). 2&3 and 
> 4&5 are the stereo pairs, but I havent figured out which pair is 
> front/surround yet.
>
> Further, if I play 5-channel content in a 6-channel environment then 
> channel 4 is empty, channel 5 plays what was in channel 4, and channel 
> 6 plays what was in channel 5 (compared with the 5-channel 
> environment). Playing 5-channel content in an 8-channel environment 
> reverts back to the configuration in the 5-channel environment, but 
> duplicates channels 1-3 on 6-8. Channel-duplication is annoying but 
> tolerable. However channel-switching is not tolerable! im working on 
> it!

>
> Mark
>
>
> On 23 Jun 2004, at 03:37, Matthew Romaine wrote:
>

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