I don't know if it's the same effect or not. We're working on an "embedded" Linux device. It has a full Linux kernel and basically is a hand-built distribution of stock Linux stuff, but is very stripped down and some of our apps are custom. As we're not using OSS in any way (neither apps nor the Alsa OSS emulation layer) so I can't speak to that.
One of our engrs here seems to think it's a hardware issue also, and the only way to get our apps to deal with it is to on the stop command push values into the pcm buffer that ramp down to 0 and then fill a full buffer-size number of samples of 0 into the buffer before closeing it. I'm not sure I agree (if it HW based, then yes I agree) and was hoping there was an approprate "alsa-way". Our device is one of those mini-itx via based boards (frequently seen mentioned on /.). It seems it uses VIA 82xx audio.
Your problem sounds more like a configuration or hardware issue, unlike ours which I'm guessing is either a hardware or actual (non-alsa) source code issue. Sorry I can't be of more help, but hopefully someone here can help, and I'll let you know what we find if anything.
Thanks, - Steve
Mark Knecht wrote:
Steve, You're the first person I can remember to report something very similar to what I'm dealing with every day. I get a huge loud cracking noise at the start of any audio operation that is not vanilla Alsa - i.e. - anything accessing OSS I think. In my case I think it's hardware based, but I'm not sure. This happens only on my HDSP 9652 system. I have two other systems, one using an onboard NForce audio device, and the other using an RME Hammerfall Light, that act correctly.
With the RME products we have the hdspconf application which shows the sync frequency of the card. I normally run at 44.1K, but if I open hdspconf and watch the card's frequency, it tells me that the card becomes unlocked and changes sample rates when the noise happens. This happens when starting any app that uses OSS (I think) like gxine, or xmms, or most games, or browsing web pages. It does not happen when starting a native Alsa application like alsaplayer.
Does this sound at all like what you're experiencing?
- Mark
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Steve deRosier Sent: Wednesday, November 19, 2003 2:15 PM To: [EMAIL PROTECTED] Subject: [Alsa-devel] Pops at start of song
All,
We're having a problem with some of our audio applications. When a song starts playing we will often hear a loud pop out of the speakers before it plays audio. It seems dependent upon where we stoped and the specfic content of the last song, if we hit our "stop control" and abort in the middle of the song it may pop uppon restarting or starting a new song.
One of our engrs found if he fills the entire buffer with zeros before quitting the program, on the next start it won't pop (though that moves the pop to the end of the previous due to a disconnect/jump in the created waveform). Unless this is a hardware issue, this doesn't seem to be the right solution to me. So:
* What are things that we can do in our program using the alsa pcm functions to eliminate this? Maybe a specific function we need to call or a particular sequence? * Or, is this something inherent in hardware and other than filling with zeros before we quit there's nothing we can do?
I figure some of you have encountered this before, so maybe there's some ideas out there?
If you're wondering what we do when a "stop" command comes in: pretty much nothing. Basically my "ALSASender" routine ends and calls: void CDSP::ClosePCM( void ) { // some other bookkeeping goes here <snip>
snd_pcm_close( hPCM );
if( mPCMStatus ) { snd_pcm_status_free( mPCMStatus ); mPCMStatus = NULL; }
// Non-alsa related cleanup goes here <snip> }
Also, note that we do get the same pops with using aplay.
Thanks, - Steve
PS Takashi -> I haven't given up on my serial driver patch, I was working on it when I got interupted with something else, it should be on its way soon; thanks for your help.
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