User talk:Balsa: Difference between revisions
(Discussed arecord and got it to record some microphone audio.) |
m (some formatting cleanup) |
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ALSA | |||
/etc/asound.names | == ALSA == | ||
/etc/asound.names<br/> | |||
Gives names and descriptions for ALSA hardware devices. Very useful when using arecord and its '-D, --device=NAME' command line options. | Gives names and descriptions for ALSA hardware devices. Very useful when using arecord and its '-D, --device=NAME' command line options. | ||
/etc/asound.conf | /etc/asound.conf<br/> | ||
I do not know what this is currently. | I do not know what this is currently. | ||
/etc/asound.state | /etc/asound.state<br/> | ||
Ditto. | Ditto. | ||
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sox - "Sound eXchange, the Swiss Army knife of audio manipulation" - (man sox; GNU General Public License) | sox - "Sound eXchange, the Swiss Army knife of audio manipulation" - (man sox; GNU General Public License) | ||
strace -e file arecord -v -d 5 -t au test4.au ----> <snip> | strace -e file arecord -v -d 5 -t au test4.au ----> <snip><br/> | ||
Recording Sparc Audio 'test4.au' : Unsigned 8 bit, Rate 8000 Hz, Mono <snip> | Recording Sparc Audio 'test4.au' : Unsigned 8 bit, Rate 8000 Hz, Mono <snip><br/> | ||
Very interesting, indeed. This gives us the default ALSA device used by arecord, in my case it was /dev/snd/pcmC0D0c. Cross referencing with /etc/asound.names doesn't get us far, because I still don't know the mappings between that file and the stuff in /dev/snd. Some speculation may be in order. | Very interesting, indeed. This gives us the default ALSA device used by arecord, in my case it was /dev/snd/pcmC0D0c. Cross referencing with /etc/asound.names doesn't get us far, because I still don't know the mappings between that file and the stuff in /dev/snd. Some speculation may be in order. | ||
grep -i capture -B 1 /etc/asound.names --> | grep -i capture -B 1 /etc/asound.names --> <br/> | ||
name 'hw:0,4' | name 'hw:0,4'<br/> | ||
comment 'Physical Device - ALC268 Analog (Capture)' | comment 'Physical Device - ALC268 Analog (Capture)'<br/> | ||
-- | --<br/> | ||
name 'plughw:0,4' | name 'plughw:0,4'<br/> | ||
comment 'Physical Device With Conversions - ALC268 Analog (Capture)' | comment 'Physical Device With Conversions - ALC268 Analog (Capture)'<br/> | ||
Hmm. | Hmm. | ||
Lets try: strace -e file arecord -v -d 5 -t au -D hw:0,4 test5.au | Lets try: strace -e file arecord -v -d 5 -t au -D hw:0,4 test5.au<br/> | ||
This opens /dev/snd/pcmC0D4c, and says "Recording Sparc Audio 'test5.au' : Unsigned 8 bit, Rate 8000 Hz, Mono" but exits with "arecord: set_params:954: Sample format non available". | This opens /dev/snd/pcmC0D4c, and says "Recording Sparc Audio 'test5.au' : Unsigned 8 bit, Rate 8000 Hz, Mono" but exits with "arecord: set_params:954: Sample format non available". | ||
strace -e file arecord -v -d 5 -t au -D hw:0,0 test5.au | strace -e file arecord -v -d 5 -t au -D hw:0,0 test5.au<br/> | ||
Same deal, but opens /dev/snd/pcmC0D0c instead. Strange, since that is the same as the default. | Same deal, but opens /dev/snd/pcmC0D0c instead. Strange, since that is the same as the default. | ||
TODO: Look at source code. Edit: nevermind. | TODO: Look at source code. Edit: nevermind. | ||
Let's try one more thing - that /etc/asound.names gave me an idea... | Let's try one more thing - that /etc/asound.names gave me an idea...<br/> | ||
strace -e file arecord -v -d 5 -t au -D plughw:0,0 test5.au | strace -e file arecord -v -d 5 -t au -D plughw:0,0 test5.au<br/> | ||
Hot dog it worked! | Hot dog it worked!<br/> | ||
open("/dev/snd/pcmC0D0c", O_RDWR|O_NONBLOCK) = 4 | open("/dev/snd/pcmC0D0c", O_RDWR|O_NONBLOCK) = 4<br/> | ||
open("test5.au", O_WRONLY|O_CREAT|O_LARGEFILE, 0644) = 3 | open("test5.au", O_WRONLY|O_CREAT|O_LARGEFILE, 0644) = 3<br/> | ||
sox test5.au -d --> Lots of clipping, noisy. | sox test5.au -d --> Lots of clipping, noisy.<br/> | ||
sox au: header size 24 is too small | sox au: header size 24 is too small | ||
Input File : 'test5.au' | Input File : 'test5.au'<br/> | ||
Channels : 1 | Channels : 1<br/> | ||
Sample Rate : 8000 | Sample Rate : 8000<br/> | ||
Precision : 8-bit | Precision : 8-bit<br/> | ||
Duration : 00:05.00 = 40000 samples ~ 375 CDDA sectors | Duration : 00:05.00 = 40000 samples ~ 375 CDDA sectors<br/> | ||
Sample Encoding: 8-bit Signed Integer PCM | Sample Encoding: 8-bit Signed Integer PCM<br/> | ||
100% 00:05.00 [00:00.00] of 00:05.00 Out:240k [!=====|=====!]Hd:0.0 Clip:182k | 100% 00:05.00 [00:00.00] of 00:05.00 Out:240k [!=====|=====!]Hd:0.0 Clip:182k<br/> | ||
sox effects: rate clipped 120593 samples; decrease volume? | sox effects: rate clipped 120593 samples; decrease volume?<br/> | ||
sox sox: alsa: output clipped 61507 samples; decrease volume? | sox sox: alsa: output clipped 61507 samples; decrease volume?<br/> | ||
Done. | Done.<br/> | ||
Aha! The recording is unsigned 8bit, but the playback was signed 8bit. How does one change this? | Aha! The recording is unsigned 8bit, but the playback was signed 8bit. How does one change this? | ||
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man sox | man sox | ||
sox -u test5.au -d | sox -u test5.au -d<br/> | ||
sox formats_i: `test5.au': overriding encoding type | sox formats_i: `test5.au': overriding encoding type<br/> | ||
Sample Encoding: 8-bit Unsigned Integer PCM | Sample Encoding: 8-bit Unsigned Integer PCM<br/> | ||
OK, it plays as unsigned 8bit. Success. | OK, it plays as unsigned 8bit. Success.<br/> | ||
Revision as of 03:36, 4 February 2011
Hi.
Balsa 03:28, 3 February 2011 (EST)
ALSA
/etc/asound.names
Gives names and descriptions for ALSA hardware devices. Very useful when using arecord and its '-D, --device=NAME' command line options.
/etc/asound.conf
I do not know what this is currently.
/etc/asound.state
Ditto.
strace - handy utility to see what programs are doing. strace -e file [some program and its args if relevant] - only shows file related stuff.
arecord - ALSA utility to record sound. It's what I'm having trouble with, and is the subject of most of this page.
sox - "Sound eXchange, the Swiss Army knife of audio manipulation" - (man sox; GNU General Public License)
strace -e file arecord -v -d 5 -t au test4.au ----> <snip>
Recording Sparc Audio 'test4.au' : Unsigned 8 bit, Rate 8000 Hz, Mono <snip>
Very interesting, indeed. This gives us the default ALSA device used by arecord, in my case it was /dev/snd/pcmC0D0c. Cross referencing with /etc/asound.names doesn't get us far, because I still don't know the mappings between that file and the stuff in /dev/snd. Some speculation may be in order.
grep -i capture -B 1 /etc/asound.names -->
name 'hw:0,4'
comment 'Physical Device - ALC268 Analog (Capture)'
--
name 'plughw:0,4'
comment 'Physical Device With Conversions - ALC268 Analog (Capture)'
Hmm.
Lets try: strace -e file arecord -v -d 5 -t au -D hw:0,4 test5.au
This opens /dev/snd/pcmC0D4c, and says "Recording Sparc Audio 'test5.au' : Unsigned 8 bit, Rate 8000 Hz, Mono" but exits with "arecord: set_params:954: Sample format non available".
strace -e file arecord -v -d 5 -t au -D hw:0,0 test5.au
Same deal, but opens /dev/snd/pcmC0D0c instead. Strange, since that is the same as the default.
TODO: Look at source code. Edit: nevermind.
Let's try one more thing - that /etc/asound.names gave me an idea...
strace -e file arecord -v -d 5 -t au -D plughw:0,0 test5.au
Hot dog it worked!
open("/dev/snd/pcmC0D0c", O_RDWR|O_NONBLOCK) = 4
open("test5.au", O_WRONLY|O_CREAT|O_LARGEFILE, 0644) = 3
sox test5.au -d --> Lots of clipping, noisy.
sox au: header size 24 is too small
Input File : 'test5.au'
Channels : 1
Sample Rate : 8000
Precision : 8-bit
Duration : 00:05.00 = 40000 samples ~ 375 CDDA sectors
Sample Encoding: 8-bit Signed Integer PCM
100% 00:05.00 [00:00.00] of 00:05.00 Out:240k [!=====|=====!]Hd:0.0 Clip:182k
sox effects: rate clipped 120593 samples; decrease volume?
sox sox: alsa: output clipped 61507 samples; decrease volume?
Done.
Aha! The recording is unsigned 8bit, but the playback was signed 8bit. How does one change this?
man sox
sox -u test5.au -d
sox formats_i: `test5.au': overriding encoding type
Sample Encoding: 8-bit Unsigned Integer PCM
OK, it plays as unsigned 8bit. Success.