Feature #3400: mobile: implement GAPK based audio capture / playback (via ALSA) - OsmocomBB - Open Source Mobile Communications

mobile: implement GAPK based audio capture / playback (via ALSA)

Added by fixeria over 2 years ago. Updated over 2 years ago.

Status:

Stalled

Priority:

Normal

Assignee:

fixeria

Category:

OsmocomBB mobile (host)

Target version:

GAPK (GSM Audio Pocket Knife) back-end intergation

Start date:

07/17/2018

Due date:

% Done:

50%

Resolution:

Spec Reference:

Description

There is an initial implementation of GAPK based audio back-end in fixeria/audio.

The current implementation is limited, so TODO/FIXME:

init both I/O processing chains when CHANNEL MODE MODIFY is received,
deinit both I/O chains when a call is finished,
take care about PHY specific frame formats (e.g. TI),
optimize the application loop in order to improve performance,
support other than GSM FR codecs (currently FR is hardcoded),
compose codec support in Classmark depending on PHY capabilities and GAPK codec support.

Some points require a possibility to know the PHY features, such as:

TCH frame forwarding capability,
preferred TCH frame format,
full rate / half rate channel support,
AMR codec over FR / HR channel support.

Checklist

Init both I/O processing chains when CHANNEL MODE MODIFY is received
Support other than GSM FR codecs (currently FR is hardcoded)
Deinit both I/O chains when a call is finished
Optimize the application loop in order to improve performance
Take care about PHY specific frame formats (e.g. TI)
Compose codec support in Classmark depending on PHY capabilities and GAPK codec support
Investigate the problem with unpleasant audio effects

Related issues

History

#1 Updated by fixeria over 2 years ago

Tracker changed from Bug to Feature

#2 Updated by fixeria over 2 years ago

Blocked by Feature #1461: include some version information / negotiation in the L1CTL protocol added

#3 Updated by fixeria over 2 years ago

Checklist item Init both I/O processing chains when CHANNEL MODE MODIFY is received added
Checklist item Support other than GSM FR codecs (currently FR is hardcoded) added
Checklist item Deinit both I/O chains when a call is finished added
Checklist item Take care about PHY specific frame formats (e.g. TI) added
Checklist item Optimize the application loop in order to improve performance added
Checklist item Compose codec support in Classmark depending on PHY capabilities and GAPK codec support added

#4 Updated by fixeria over 2 years ago

Status changed from New to In Progress
% Done changed from 0 to 50

#5 Updated by fixeria over 2 years ago

Checklist item Optimize the application loop in order to improve performance set to Done

The performance problem is actually caused by blocking calls of src/pq_alsa.c/pq_cb_alsa_input()/snd_pcm_readi().
Setting both buffer and period size values seems to solve the issue. A separate issue needs to be created...