[alsa-devel] Noisy audio - ALSA Configuration
Eliot, Thank you very much. Here is the message. If Hotmail is the problem I can subscribe using my work e-mail; I wanted to avoid that in the first place. Magdalena
The Hotmail message is all HTML, with no plaintext version. I'm not sure if this list accpets html mails. OR The text of the mail is all encapsulated in a number of HTML <DIV> blocks, maybe confused html to text converter...
Here is the original question:
Does anyone have examples or documentation on how to configure periods, frames and buffers for various sample rates? I am writing a program to route a mp3 decoder output to ALSA on an ARM processor, and I get noisy audio. For a CD quality stream (S16_LE, 44100 kHz, Stereo, 128 bps) I am using an output buffer of 44100 bytes, a period of 44100/(channels*2). With
Be careful about the distinction between bytes and frames (i.e. a frame of stereo S16 is 4 bytes)
Start with the period 1024 frames = 4096 bytes then make your buffer at least 2x this: 8192 bytes
(I'm not an app developer, so others may jump in with a better explanation)
Did you look at the code in alsa-lib/test?
a buffer this big, I do not get underruns, but I do get all short writes. I have not been able to find the right configuration to avoid short writes, and more importantly, to get good quality audio. What do 'short writes' (I am using writei) really mean? Is this a performance issue in the driver, or is mainly because of buffer setup? I would really appreciate any help with this. Magdalena
participants (2)
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Eliot Blennerhassett
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Magdalena Iovescu