Underlying debugging of Android audio-Based on tinyalsa and androidtinyalsa

Underlying debugging of Android audio-Based on tinyalsa and androidtinyalsa

By default, standard alsa is not used in Android, but tinyalsa is used. Therefore, libtinyalsa is used for command line-based testing. The Android system can view these tools in real time when the upper-layer Audio is ever changing, such as switching the Audio channel.

 

1. Compile the tinyalsa Tool

$ Mmm external/tinyalsa/

After compilation, tinyplay, tinymix, tinycap, and other tools will be generated.

Tinymix: View configuration Mixer

Tinyplay: play audio

Tinycap: Recording

 

2. view the sound card of the current system

root@android:/ # cat /proc/asound/cards 0 [RKRK616        ]: RK_RK616 - RK_RK616                      RK_RK616 1 [ROCKCHIPSPDIF  ]: ROCKCHIP-SPDIF - ROCKCHIP-SPDIF                      ROCKCHIP-SPDIFroot@android:/ # 

3. tinymix

Tinymix usage method a. Without any parameters-display the current configuration B. tinymix [ctrl id] [var] without [var]. You can view the [ctrl id] Option.

root@android:/ # tinymixNumber of controls: 7ctltypenumname                                     value0ENUM1Playback Path                            OFF1ENUM1Capture MIC Path                         MIC OFF2ENUM1Voice Call Path                          OFF3ENUM1Voip Path                                OFF4INT2Speaker Playback Volume                  0 05INT2Headphone Playback Volume                0 06ENUM1Modem Input Enable                       ONroot@android:/ #

Explanation:

English	Chinese	Remarks
Playback Path	Audio output channel
Capture MIC Path	Audio input channel
Voice Call APIs	Call audio channel	Unable to test because the device does not have a call module
Voip APIs	IP telephone audio channel	Scenario Gtalk; values: SPK/HP_NO_MIC/BT
Speaker Playback Volume	Speaker volume	It is irrelevant to the upper volume.
Headphone Playback Volume	Earphone volume	Same as above
Modem Input Enable	I do not know how to use it	Tested, audio input and output cannot be controlled.

Playback Path:

English	Chinese	Remarks
OFF	Close
RCV	-
SPK	Speaker	Common
HP	Ear belt microphone
HP_NO_MIC	Headset without microphone	Common
BT	Bluetooth
SPK_HP	-
RING_SPK	-
RING_HP	-
RING_HP_NO_MIC	-
RING_SPK_HP	-

For example, switch the output to the speaker.

Root @ android:/# tinymix 0 SPK

Summary of tinymix:

It is observed that the Android system does not directly use tinyalsa to adjust the sound volume, but is implemented based on the upper-layer software because no matter how the upper-layer volume changes, here we see 24 (taking the device I used as an example ). Channel switching is actually using tinyalsa. When playing music through different channels, you can observe the channel switching in real time. On a website, we can see that Android will talk about alsa 3 seconds after there is no sound playing. It is also confirmed that I used to think that the Android system will occupy the audio device permanently.

When playing music through Bluetooth, it is no longer through alsa. Tinymix can be viewed in a closed state, because all the Bluetooth protocols of Android4.2 are implemented at the user layer, and the uart channel is used directly. This design will be incomprehensible at half past one.

 

4. Use tinyplay to play wav music

This is just the most basic player, so it does not support playing MP3 and other compressed formats of music. Before I learned how to use it, I said it was very troublesome on the Internet, but now it seems that it is not troublesome to play the 44.1 kHz/44.8kHz wav music directly.

root@android:/ # tinyplay /sdcard/0_16.wav                                     Playing sample: 2 ch, 44100 hz, 16 bitroot@android:/ # 

Note: Before playing a video, you must first set the channel using tinymix. An example has been provided in the previous article to set the channel to the speaker. Since the maximum volume used for playing a video, so be sure to avoid being scared. Upload the audio file.

 

5. tinycap usage

Root @ android:/# tinycap/sdcard/test.wav

Recording is supported.

 

If you only encounter these problems at present, we can summarize them first, so that you can go deeper at any time.

Other assumptions confirmed as false:

1. init. rc needs to be rewritten so that the system does not start android-related services (mediaserver)

2. tinyalsa needs to be obtained through other channels.

Android underlying development problems?

Android underlying layer?
Do you mean android platform code development or development of android scripts and version control?
For android platform code development:
Download the source code from the google website and study the underlying Java basics.
If you want to develop scripts, version control, or C code at the bottom of android:
Then you need to be very familiar with C and have a good understanding of the android source code structure, and you need to understand JNI and other technologies.

I wrote an android underlying driver. How can I debug it?

There are two types: one is the driver implemented in the kernel, which is no different from the general linux kernel driver, and there is nothing special about debugging, such as printk plus printing and debug fs. Another kind of driver is implemented at the Hal layer, and it is also a log, maybe debug fs is not used