AC3 Audio Fun

[mvallevand]

You know, I haven't really played much with this, but it might be time. Would you say that you don't want on- the- fly transcoding, because the transcoder may drop the multichannel sound, or downmix it?

There are two reasons, with AC3 passthru it is pretty clear why, for the internally downmixed audio I don't want to lose valid time stamp information.

From my perspective I would want to see ZProcess work with mvpmc, but haven't really tried yet. I have built 6 channel sound into ZProcess but haven't been able to use it yet because of the MVP being 2 channel only , til now...

For digiital out only. It might be a good marriage with all the xvid/ac3 mp4/ac3 and HD/ac3 files. ZProcess might even insert key frames to help me correct the current a/v sync issues.

Martin

[JimF]

Are you aiming to get it to work with analog output too, or is that not possible?

[mvallevand]

Are you aiming to get it to work with analog output too, or is that not possible?

Right now mvmpc does downmix to stereo on the analog output, but it could be made configurable to downmix to surround instead.

For the technically inclined mvpmc use the liba52 modules to do this. I have no idea how will the surround sound downmix sounds.

Martin

[jksmurf]

A2 Funny, the keys are on the new remote. I haven't figured out how to do this logically on the old remotes.

Oops, I never even noticed those buttons before....I HAVE the new remote :o

OK, I finally got around to trying the Movie.VOB renamed to Movie.MPG (after testing it on the PC first to make sure it ran OK there before subjecting it to the MVP. I had problems with this testing it on the PC initially, as TBH I have never played videos via GBPVR on the PC.*

In any case the Video played perfectly as expected (MPEG2) but the audio was not only widely out of sync, it was extremely choppy (via a wired MVP over a wireless WRT54GS-WRT54GS Bridge).

Don't take this as a critisicm, I know you're really pushing the boundaries here, but while it is interesing to see that it is certainly "capable" of AC3, and if the choppiness was overcome, it could possibly be used by a 5.1 afficionado keen to mash # and * a few times. (btw once synced does it STAY that way, suffice to say I didn't watch the entire movie, it was already 1:30 a.m. by the time I got that far ... ).

I really had a good go at those # and *keys.

Now, I haven't got around to sticking in the Test Dongle to get logs, but (a) Does that Test Dongle have AC3 enabled and
(b) Do you need logs or just a general comment?

* As an aside I must categorically state that Nvidia's integration of their own Audio Codec with their quite good Video Codec leaves much to be desired, at least in GBPVR, despite claiming that it can do AC3. It would play Video, but no sound. I have documented this in another (existing thread).

Cheers

k.

[mvallevand]

In any case the Video played perfectly as expected (MPEG2) but the audio was not only widely out of sync, it was extremely choppy (via a wired MVP over a wireless WRT54GS-WRT54GS Bridge).

Thanks for doing the test. Playing a vob does take a lot of bandwidth, it might be interesting for you to try an mvpmc throughput test to see what your system is capable of. If you are interested

1 place a vob or mpg in your mvpmc folder on your gbpvr server
2. instead of going into emulation go to filesystem on your mvp
3. browse to /etc/mvpmc
4. cursor to your file
5 hit the menu button and select throughput test
6. let hit play for thirty seconds
7. hit stop and record your rate

I get about 10Mbs, some mvpmc users have hit 13,

You might be interested in seeing how mvpmc native handles it too, just hit select to play it.

Don't take this as a critisicm, I know you're really pushing the boundaries here, but while it is interesing to see that it is certainly "capable" of AC3, and if the choppiness was overcome, it could possibly be used by a 5.1 afficionado keen to mash # and * a few times. (btw once synced does it STAY that way, suffice to say I didn't watch the entire movie, it was already 1:30 a.m. by the time I got that far ... ).

I don't consider it criticism. In fact the reason I called this fun is I want to see how many people can hear the audio ok before I spend time trying to sync automatically.

I really had a good go at those # and *keys.

I only use the pound/hash/octothorpe/number ? key. The asterisk is too fine.

Now, I haven't got around to sticking in the Test Dongle to get logs, but (a) Does that Test Dongle have AC3 enabled and
(b) Do you need logs or just a general comment?

a yes the mvpmc debug dongle has ac3 and the same emulation code
b comments are fine, but the throughput test would be more valuable then the logs.

Thanks again,

Martin

[jksmurf]

but the throughput test would be more valuable then the logs. Martin

6.34 mb/s. :-( I ran it for a minute...

Disappointed!!!

I have all Tipstirs network tweaks installed, maybe I need to look at Router Tweaks as it runs through 2 of those before it gets to the NIC in my PC.
WDS Mode is only 1/2 duplex I understand ...

Disappointed!!!

k.

[HtV]

It's quite a miracle the movie itself played ok, must have been not too high bitrate.
I don't know what distance there is between router and mvp, I do know that throughput can go down very quickly with increasing distance.

I guess it's time to get the drill out and roll out some cat-cable.

Hans

[mvallevand]

6.34 mb/s. :-( I ran it for a minute...

Disappointed!!!

I have all Tipstirs network tweaks installed, maybe I need to look at Router Tweaks as it runs through 2 of those before it gets to the NIC in my PC.
WDS Mode is only 1/2 duplex I understand ...

Disappointed!!!

k.

That's not a terrible bit rate but could be low for vob's. Tweaks that work for one network don't always work for another. The 1/2 duplex is more of a concern to emulation which this thruput test but it could have an impact. Again I'd be curious how it plays in mvpmc native mode.

Martin

[jksmurf]

Again I'd be curious how it plays in mvpmc native mode. Martin

1. What IS mvpmc native mode?
2. I tried Server PC <=>WRT54GS (AP) <=Wireless=> WRT54GS (Wireless Ethernet Bridge) <=> MediaMVP to get past WDS mode 1/2 duplex restriction, but I get 5.17mb/s, even less :confused: !!

k.

[mvallevand]

1. What IS mvpmc native mode?

I meant playing the file without using emulation mode. Instead of doing the throughput test just hit the OK button to play the file.

2. I tried Server PC <=>WRT54GS (AP) <=Wireless=> WRT54GS (Wireless Ethernet Bridge) <=> MediaMVP to get past WDS mode 1/2 duplex restriction, but I get 5.17mb/s, even less :confused: !!

I think with wireless network performance is difficult to quantify, and here you are adding in the complexities of the share if the server or drive is busy etc and also a test of the mvpmc demux speed with a specific mpeg file.

If you want to test the network and disk speed without testing mvpmc performance this command from telnet will do that.

time dd if=/etc/mvpmc/your.mpg of=/dev/null bs=8192 count=512

count is the number of 8k block you want to read, this is a 4 MB test. As an example from various shares I have

Vista (fast SATA) 2.10s
Maxtor MSS+ 2.18s
NSLU2 (slow PATA) 2.59s

BTW I can duplicate an error -195 on a windows share but I don't get the 0 byte file. I was testing this via my NSLU2 and obviously Samba and Windows aren't quite the same. The solution was just that the guest account didn't have the write access authorization.

Martin