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Non-loopback audio
PostPosted: Mon May 07, 2007 8:30 pm Reply with quote
kdogksu
 
Joined: 07 May 2007
Posts: 1




I've been reading this forum, but can't figure out: are you using external loopback audio or have you enabled audio over PCI? I can hear the audio when I plug the external cable into my soundcard. However, the video greatly lags the audio when watching live TV in MythTV (I assume due to buffering delay), and doesn't record when I record a program. Any suggestions?

Right now I'm just testing this with NTSC. I don't have a HD signal to test with at the moment. Any help would be appreciated.
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PostPosted: Tue Jun 12, 2007 7:54 am Reply with quote
nybbler
 
Joined: 06 Jul 2006
Posts: 125




Staudie: The nodmarestart functionality has been incorporated into the kernel. The irq loss patch is still applicable, but if you're not getting video either, you probably have a different problem.
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Analog audio quality is poor, and HD audio is non-existent
PostPosted: Wed Aug 15, 2007 10:06 am Reply with quote
underfunded
 
Joined: 10 Aug 2007
Posts: 4




Nybbler,

I'm running Ubuntu 7.04 with MythTV, and although I can get my PVR-150 to work, I can't seem to get my HD-5500. I've given up on getting HD working, besides, comcast doesn't offer alot in the way of HD content right now. 've tried everything I've read in these forums, but I don't seem to be able to get it Analog sound working to work correctly. I saw your workarounds, but I don't know how to apply them. And is there a reason my picture is cropped when watching analog. Any help you can provide would be greatly appreciated. Let me know what info you need to analyze my problem.

Thanks
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PostPosted: Wed Aug 15, 2007 1:47 pm Reply with quote
nkopas
 
Joined: 09 Aug 2007
Posts: 7




Nybbler,

I'm going to put myself in the same category as underfunded. I'm running KnoppMyth R5F1 and I've had a hell of a time trying to get analog sound working. R5F1 uses kernel 2.6.18 (or 2.6.18-chw-13-10.00 I guess). I've tried recompiling the modules using the diffs you posted as a guidline, but so far I've had no success. I echo underfunded's appreciation at any help you can provide!
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PostPosted: Wed Aug 15, 2007 7:26 pm Reply with quote
nkopas
 
Joined: 09 Aug 2007
Posts: 7




Getting analog sound working on KnoppMyth R5F1 with a pcHDTV HD-5500

cx88-alsa.diff
cx88-tvaudio.diff

Recompiling modules with patches:

1. Download kernel source from ftp://knoppmyth.net/R5/linux-source-2.6.18-chw-13_2.6.18-chw-13-10.00.Custom_all.deb

2. Install package and bunzip archive located in /usr/src/.

3. Apply the attached attached diffs to the following files:
/usr/src/linux-source-2.6.18-chw-13.tar/linux-source-2.6.18-chw-13/drivers/media/video/cx88/cx88-alsa.c
/usr/src/linux-source-2.6.18-chw-13.tar/linux-source-2.6.18-chw-13/drivers/media/video/cx88/cx88-tvaudio.c

4. Cd to /lib/modules and move 2.6.18-chw-13 to 2.6.18-chw-13.old

5. Cd to usr/src/linux-source-2.6.18-chw-13 and run "make menuconfig".

6. Scroll down and select "load an alternate configuration file".

7. Specify the file "/boot/config-2.6.18-chw-13", save and exit.

8. Run "make modules", then "make modules_install".

9. Run "depmod" and reboot.


Tweaks:

1. Add the following line to /etc/modprobe.d/alsa-base:
options cx88-alsa index=-2,-2

2. Add the following line to /etc/modprobe.d/dvb-core:
options dvb_core dvb_shutdown_timeout=0

3. Run mythtv-setup, in the Recorder Options of your DVB card, check "Open DVB card on demand".

4. Enter frontend setup, modify the recording profile for Software Encoders. Set Live TV's sampling rate to 48000.
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PostPosted: Fri Aug 17, 2007 1:31 pm Reply with quote
underfunded
 
Joined: 10 Aug 2007
Posts: 4




nkopas,

thanks for the help, I went in to the software encoder portion of Myth, and tweaked a couple of things. Thanks for the help.
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PostPosted: Sun Aug 19, 2007 2:17 pm Reply with quote
xyzzy
 
Joined: 12 Feb 2006
Posts: 225




nybbler wrote:
There are two different issues. One issue is that during a channel change, the cx88 driver stops and starts the audio DMA on the card, to avoid an audible buzz when using the NICAM standard. This ends up putting the wrong value in the audio DMA control register thereby killing ALSA audio.

It's not just NICAM, but an undocumented feature/bug that probably affects all audio standards. The analog audio output requires that the audio FIFO be on to work. It also requires that the FIFO be setup with exactly 4 buffers.

The ALSA driver uses two buffers, so if you listen to the analog output (the connector on the back of the card), it will be full of buzzing while the ALSA driver is capturing.

Quote:

There are #ifdefs in the driver which are intended to prevent this, but they don't work if you compile as modules (which is the normal case).

Starting and stopping the FIFO like this should be ok.

Quote:

The other issue is that during a switch from digital to analog or a channel change, the card sometimes just spews audio interrupts.

I think I have a real fix for this problem:
http://linuxtv.org/hg/~tap/v4l-dvb/rev/3dfe9696a213

The problem is that video driver turns the audio FIFO on, so that the analog output will work. Because of this the FIFO will be in use when the ALSA driver re-configures it, and one gets many FIFO sync errors.
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PostPosted: Fri Aug 24, 2007 5:56 am Reply with quote
nkopas
 
Joined: 09 Aug 2007
Posts: 7




xyzzy wrote:
I think I have a real fix for this problem:
http://linuxtv.org/hg/~tap/v4l-dvb/rev/3dfe9696a213

xyzzy,

the above link doesn't work, but i was able to browse and see that you've made a lot of tweaks to the code. Can you point out which changes you reccomend I try to apply to the version on my box? Or better yet, do you have a link to download your current version of all the cx88 stuff?

thanks
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PostPosted: Sun Sep 09, 2007 1:13 pm Reply with quote
whistl
 
Joined: 09 Sep 2007
Posts: 1




mhitchens wrote:
cfr131 wrote:
I have the analog sound working, but the quality is very bad. It sounds like a 56kbs MP3, with lots of compression artificts. I don't know where to look to see why there is compresion occuring.


Not sure if you've solved this one yet, but I had a similar issue. It ended up being that the default sampling rate for live TV in MythTV was 32000, and not 48000. Changing made it clear as day.

To get there, it's in Recording Profiles -> Software Encoders -> LiveTV, then just set up the encoding options, audio is on the second page.

Hope that fixes it for you!


I want to thank you, as this was the final hurdle getting NTSC analog sound working on my PChdtv 5500 in MythTV.

In case you are still struggling, in mythtv-setup, I configured the card as "Analog V4L capture card", and changed audio device to "/dev/dsp1".

Then, after starting mythbackend -d and mythfrontend, in "setup", under "TV Settings", I followed the above instructions, entering recording profiles, software encoders, livetv, and setting the sampling rate to 48000. Now audio starts playing when I start watching tv, and it even appears to be sync'd to the video (unlike when I was using tvtime).

Woo Hoo!

Now I'm off to installed a high gain antenna so I can use my second card for ATSC broadcast channels.
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PostPosted: Mon Sep 10, 2007 1:13 pm Reply with quote
nybbler
 
Joined: 06 Jul 2006
Posts: 125




Quote:

Starting and stopping the FIFO like this should be ok.

And would be, except that in doing so, it also turns off the RISC sequencer. Fortunately this has been fixed.

Quote:

I think I have a real fix for this problem:
http://linuxtv.org/hg/~tap/v4l-dvb/rev/3dfe9696a213

The problem is that video driver turns the audio FIFO on, so that the analog output will work. Because of this the FIFO will be in use when the ALSA driver re-configures it, and one gets many FIFO sync errors.


Ahh, great. That one's been bugging me for a long while.
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PostPosted: Sat Sep 15, 2007 4:23 pm Reply with quote
xyzzy
 
Joined: 12 Feb 2006
Posts: 225




It turns out the sync errors when starting audio DMA aren't totally fixed. They do not appear to happen very often now, but if I setup a script to change channels and start dma I can get an error many every 100 tries.

I think I understand how the analog audio out works better now. The cx88 is playing back audio from the upsteam DMA channel.

Of course the cx88-alsa driver doesn't support playback, and when the alsa driver isn't loaded there isn't any audio dma going on at all. So where is the upsteam DMA comming from? What the driver does is set the upsteam FIFO to be in the same place in the SRAM as the downstream FIFO. The audio decoder is putting audio data into the downsteam FIFO and the internal DAC is taking the audio data from the same spot as if it was coming from host via DMA. This is why one gets distorted sound if the downsteam FIFO buffers aren't configured the exact same way as the upstream FIFO buffers.

I've got one theory that playback modifies the various internal FIFO fields, as does audio downsteam DMA. While it obviously works ok for both to be going on at once, maybe there is a problem when the downsteam FIFO configuration is modified while playback is on? Since the downstream and upstream FIFO are one and the same.
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PostPosted: Thu Oct 25, 2007 10:26 am Reply with quote
hizoomi
 
Joined: 25 Oct 2007
Posts: 1




nkopas wrote:
xyzzy wrote:
I think I have a real fix for this problem:
http://linuxtv.org/hg/~tap/v4l-dvb/rev/3dfe9696a213


xyzzy,

the above link doesn't work, but i was able to browse and see that you've made a lot of tweaks to the code. Can you point out which changes you reccomend I try to apply to the version on my box? Or better yet, do you have a link to download your current version of all the cx88 stuff?

thanks


xyzzy,

I found the following; is this the fix you refer to above?

http://linuxtv.org/hg/~tap/v4l-dvb/rev/31860d2a60bf

After tweaking the eeprom I was able to get my HD-3000 delivering audio via PCI without the external loopback cable (yay!), and after changing the sample rate to 48000 via the frontend TV menus as mentioned elsewhere (should this also be done in mythtv-setup for the capture card so that recording will work properly?), the sound is better but not perfect, presumably because I still haven't done either of the cx88-alsa patches yet. (I'm using mythtv on Ubuntu and haven't yet looked hard enough for which software package has the driver source I need.)

I haven't seen any problems with changing channels while watching live TV, so presumably the cx88-tvaudio patch isn't needed.

Thanks,

Charles
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64 bit version? Are fixes integrated into driver?
PostPosted: Wed Jul 08, 2009 4:06 pm Reply with quote
mholtz
 
Joined: 07 Jul 2009
Posts: 2




Hello,

I am using a pcHDTV3000 card, and apparently I also have the analog audio disabled, so I'd like to update my EEPROM. I am running 64 bit AMD, so I cannot run the 32 bit code. Can you please provide the source, or else recompile it for 64 bit?

Also, what is the status of the driver patches you posted? Have these been integrated into the Linux kernel drivers?
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5500 analog audio device? driver?
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