[mythtv-users] CX88 "Blackbird" audio razziness

raphael rpooser at gmail.com
Fri Mar 2 16:24:52 UTC 2007

Rod Smith wrote:
> On Thursday 01 March 2007 12:54, Dennis Hand wrote:
>>> I used the standard drivers in the kernel; I haven't tried
>>> anything from the v4l site itself. If you try that approach and don't
>>> have the audio problems, I'd love to hear about it.
>> I believe one of the new things in the v4l code is that they have made
>> the Avermedia M150 use the standard firmware instead of the one your
>> referring to. From the v4l ChangeLog.
> I might look into it, then; it could be my audio problems are 
> firmware-related. OTOH, I did initially try the firmware pointed to by the 
> v4l site, but it didn't work. The drivers initially tried loading the 
> 376,836-byte image, but that failed. A posting I found online suggested 
> renaming the firmware, so I tried the 262,144-byte image, but that also 
> failed with a message about checksum errors, IIRC. It was only when I tried 
> the firmware from the site described in my wiki entry that the MPEG encoder 
> started working. This makes me suspicious that the card might not work with 
> the firmware for other Blackbird-based cards, but I can't be sure of that. 
> Perhaps the driver was just squawking over a combination it wasn't programmed 
> to recognize or something.
> In any event, if you try the updated v4l drivers, please report back. I might 
> not get around to trying them for a few days, since I'm using the card as a 
> second tuner, and in that role the audio bug doesn't seem to crop up very 
> often. Therefore I'm in no rush to spend more hours experimenting with it. 
> For a $5.50 eBay purchase ($13.49 shipped), I'm satisfied even if it never 
> works better than it does now....
The sound "razziness" issue is not just a problem with the avermedia 
card. I've seen it with other cx88 configurations as well, including 
software tuners. I had this sound issue and tried all manner of things 
to solve it. None of the cx88 drivers I tried worked, those in the 
kernel or those in v4l.
The problem only showed up when I switched from using my discrete sound 
card to using my onboard sound. I may not have done enough testing to 
see if it happens with the discrete card or not though. The probability 
of the problem occuring is quite low, but in my case seemed to have 
something to do with how long the machine was up, or perhaps how much 
time the card spent recording. Once it happens, a reload of the drivers 
is needed to fix it. I decided that until the problem is fixed, I would 
simply reload the drivers after a set period of time, reducing the 
probability of it happening. If it was recording when the script 
attempted to reload the drivers, it just silently returned an error that 
went to null. It ran every hour, and since then I never had an razy 
recordings. Of course, I upgraded to a pvr-150 later, so I can't vouch 
on using this unelegant method for long term purposes on a primary 
tuner. I'm just mentioning this because if all else fails, you can try 
this to at least turn this useless tuner into a useful
secondary one.

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