Bryan Ischo wrote: > Here is a technique I have tried to reduce the effect of underrun. In > my application, underrun either means that the process that is > generating audio can't keep up (it's a game emulator, generating audio > and video frames at a fixed rate, and some games can't be emulated at > full speed and so don't generate audio fast enough, and in that case, > the user experience is not going to be great; I'd rather have choppy > audio than pops though so this is why I tried the following technique): > > snd_pcm_sw_params_get_boundary(sw_params, &boundary); > snd_pcm_sw_params_set_stop_threshold(pcmM, sw_params, boundary); > snd_pcm_sw_params_set_silence_threshold(pcmM, sw_params, 0); > snd_pcm_sw_params_set_silence_size(pcmM, sw_params, boundary); > > The idea here is to play silence on underrun instead of looping (which > sounds bad), and also to avoid having to re-prepare the device after > underrun which takes time and only compounds the performance problem > that is resulting in underruns. > > The thing is, this technique didn't work on some hardware - once ALSA > played silence instead of underrunning one time, it never would play > anything again. If an underrun happens, you have to catch up, i.e., you have to write all the data even though it was not played. This works only if there was a temporary delay, not if the generated audio is consistently too slow. You can avoid generating that data by checking for an underrun (snd_pcm_avail will be larger than the buffer size) and skipping over the lost part of the buffer (snd_pcm_forward, if supported, or just write zeroes ). Regards, Clemens ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
