In MMAP access mode, we write directly to a memory pointer.
In the LG-ARM device, when using non-MMAP mode, it looks like jitters
are caused by the player overwriting the ALSA buffer.
When the buffer is full the application should not write into the
buffer, otherwise it will overwrite old samples. This looks like what
the application is doing.
Thanks,
Deepak Jain
Eric Hyche wrote:
Change looks fine, but I'd like to understand more the differences between the two modes
and why MMAP access mode fixes this particular problem. Can you tell me the difference
between these two access modes and why MMAP access mode is preferable for LG-ARM? Why
does changing the access mode fix this problem of audio "jitters" at startup?
Eric
On Jan 12, 2010, at 6:56 AM, Deepak Jain wrote:
Project: Real Player for MID - ARM.
Synopsis: Fix for audio jitters on audio start-up on LG-MID ARM device
Overview: When we play any file on LG-MID ARM device, we hear small audio
jitters during playback startup. These jitters remain for 2-3 seconds and after
that the audio jitters go away.
Currently we are using RW access mode. If we use MMAP access mode, and then
instead of snd_pcm_writei() API, use snd_pcm_mmap_writei() API in
_WriteBytes(), we do not hear any jitters on start-up.
A new config define HELIX_CONFIG_PCM_MMAP is applied for enabling/disabling
mmap mode.
Files Modified:
audio/device/platform/unix/audlinux_alsa.cpp
Image Size and Heap Use impact (Client -Only):
None.
Platforms and Profiles Affected:
None.
Distribution Libraries Affected:
None.
Distribution library impact and planned action:
None.
Platforms and Profiles Build Verified:
BIF: hxclient_3_4_11_atlas_restricted
Target: player_mid_all_installers
Profile: helix-client-mid-arm
Branch:
Atlas_3411
Files Attached:
audlinux_alsa.diff
Thanks,
Deepak Jain
<audlinux_alsa.diff><ATT00001..txt>
Eric Hyche ([email protected])
Principal Engineer
RealNetworks, Inc.
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