Changes between Version 4 and Version 5 of Capture/ALSA

Timestamp:

Jun 5, 2014, 7:14:30 PM (12 years ago)

Author:

llogan

Comment:

minor formatting

Capture/ALSA

@@ -3 +3 @@
 = Syntax =
 
-Capturing audio with FFmpeg and ALSA is pretty much straightforward. Usual way to do this is like this:
+Capturing audio with `ffmpeg` and ALSA is pretty much straightforward:
 {{{
 ffmpeg -f alsa <input_options> -i <input_device> ... output.wav
 }}}
 
+See the [https://ffmpeg.org/ffmpeg-devices.html#alsa FFmpeg ALSA input device documentation] for more info.
+
 = Selecting the input card =
 
-'''input_device''' tells FFmpeg which audio capturing card`/`device you would like to use. To get the list of all installed cards on your machine, you can type '''arecord -l''' (small L) or '''arecord -L''' (longer output).
+`input_device` tells `ffmpeg` which audio capturing card or device you would like to use. To get the list of all installed cards on your machine, you can type `arecord -l` or `arecord -L` (longer output).
 
-So, first, list your recording cards/devices:
+To list recording cards or devices:
 {{{
-# arecord -l
+$ arecord -l
 
 **** List of CAPTURE Hardware Devices ****
@@ -34 +36 @@
 }}}
 
-We can see there are 2 audio cards installed that provide capturing capabilities, namely "'''card 0'''" (Intel ICH5) and "'''card 1'''" (Microphone on the USB web cam). The easiest thing to do is to reference each of them directly using "'''-f alsa -i hw:0'''" or "'''-f alsa -i hw:1'''":
+We can see there are 2 audio cards installed that provide capturing capabilities, namely "card 0" (Intel ICH5) and "card 1" (Microphone on the USB web cam). The easiest thing to do is to reference each of them directly using `-f alsa -i hw:0` or `-f alsa -i hw:1`:
 {{{
 ffmpeg -f alsa -i hw:1 -t 30 out.wav
 }}}
-That will give us a 30 seconds WAV audio output, recorded from our USB camera's '''default recording device''' (microphone). The default recording device can be selected using "alsamixer" tool (see below) or specifying the device using an additional parameter Y in '''hw:<X>,<Y>''', where <X>=card, <Y>=device. For example, to select "MIC2 ADC" from Intel card (look above at the list), we would use:
+That will give us a 30 seconds WAV audio output, recorded from our USB camera's '''default recording device''' (microphone). The default recording device can be selected using the `alsamixer` tool (see below) or specifying the device using an additional parameter Y in `hw:<X>,<Y>`, where <X>=card, <Y>=device. For example, to select "MIC2 ADC" from Intel card (look above at the list), we would use:
 {{{
 ffmpeg -f alsa -i hw:0,2 -t 30 out.wav
 }}}
-The best way is to select your card and default recording device with "alsamixer" tool, because some audio cards have a complicated way of selecting the default input through the FFmpeg's command line.
+The best way is to select your card and default recording device with the `alsamixer` tool, because some audio cards have a complicated way of selecting the default input through the `ffmpeg` command line.
 
 == Surviving the reboot ==
 
-If you reboot your machine, you will notice sometimes your cards get reordered, so "card 0" is listed as USB Audio and "card 1" is listed as Intel audio card. You might want to play with [http://www.reactivated.net/writing_udev_rules.html udev rules], but there is an easier solution for this. Typing '''arecord -L''' will give us a little bit more detailed listing of recording devices:
+If you reboot your machine, you will notice sometimes your cards get reordered, so "card 0" is listed as USB Audio and "card 1" is listed as Intel audio card. You might want to play with [http://www.reactivated.net/writing_udev_rules.html udev rules], but there is an easier solution for this. Typing `arecord -L` will give us a little bit more detailed listing of recording devices:
 {{{
 #!html
@@ -104 +106 @@
 }}}
 
-We can tell FFmpeg exactly what card we want to use, specifying the exact card's name, no matter which ordering it is, like this:
+We can tell `ffmpeg` exactly what card we want to use, specifying the exact card's name, no matter which ordering it is, like this:
 {{{
 #!html
@@ -115 +117 @@
 == ALSA mixer tool ==
 
-You might find useful a tool named '''alsamixer'''.
+You might find useful a tool named `alsamixer`.
 
 [[Image(alsamixer.png)]]
 
-It will let you visually select, for each specified card (intel or usb), which recording device do you want to use (if the specified card has got multiple inputs, like Line-In, CD-In, Mic, ...), so you can just run "alsamixer", press F6 to choose the card and then use TAB key to switch to recording devices (pressing it multiple times just switches between playback/recording/all devices), after that just use arrow keys to highlight desired device and just hit the SPACEBAR key to select it (and up/down, page up/dn keys to change the input volume).
+It will let you visually select, for each specified card (Intel or USB), which recording device do you want to use (if the specified card has got multiple inputs, like Line-In, CD-In, Mic, etc), so you can just run `alsamixer`, press F6 to choose the card, and then use TAB key to switch to recording devices (pressing it multiple times just switches between playback/recording/all devices), after that just use arrow keys to highlight desired device and just hit the SPACEBAR key to select it (and up/down, page up/dn keys to change the input volume).
 
 = Input options =
 
-The only useful [http://ffmpeg.org/ffmpeg.html#Audio-Options audio input options] for ALSA input are "-ar" (audio sample rate) and "-ac" (audio channels).
+The only useful [https://ffmpeg.org/ffmpeg.html#Audio-Options audio input options] for ALSA input are `-ar` (audio sample rate) and `-ac` (audio channels).
 
 Specifying audio sampling rate/frequency will force the audio card to record the audio at that specified rate. Usually the default value is "44100" (Hz).
@@ -132 +134 @@
 == Grab an audio from your microphone ==
 
-When doing screencast recordings, you usually want to record your voice too, so you would probably want to do something like this:
+When doing screencast recordings, you usually want to record your voice too:
 {{{
 ffmpeg -f alsa -ac 1 -ar 44100 -i hw:0 -t 30 out.wav