Re: [PATCH v4 1/3] ALSA: compress: document the compress audio state machine
From: Amadeusz SÅawiÅski
Date: Mon Jun 29 2020 - 15:28:11 EST
On 6/29/2020 9:50 AM, Vinod Koul wrote:
So we had some discussions of the stream states, so I thought it is a
good idea to document the state transitions, so add it documentation
Reviewed-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
---
.../sound/designs/compress-offload.rst | 51 +++++++++++++++++++
1 file changed, 51 insertions(+)
diff --git a/Documentation/sound/designs/compress-offload.rst b/Documentation/sound/designs/compress-offload.rst
index ad4bfbdacc83..b6e9025ae105 100644
--- a/Documentation/sound/designs/compress-offload.rst
+++ b/Documentation/sound/designs/compress-offload.rst
@@ -151,6 +151,57 @@ Modifications include:
- Addition of encoding options when required (derived from OpenMAX IL)
- Addition of rateControlSupported (missing in OpenMAX AL)
+State Machine
+=============
+
+The compressed audio stream state machine is described below ::
+
+ +----------+
+ | |
+ | OPEN |
+ | |
+ +----------+
+ |
+ |
+ | compr_set_params()
+ |
+ v
+ compr_free() +----------+
+ +------------------------------------| |
+ | | SETUP |
+ | +------------------------>| |<-------------------------+
+ | | compr_drain_notify() +----------+ |
+ | | or ^ |
+ | | compr_stop() | |
+ | | | compr_write() |
+ | | | |
+ | | | |
+ | | +----------+ |
+ | | | | compr_free() |
+ | | | PREPARE |---------------> A |
+ | | | | |
+ | | +----------+ |
+ | | | |
+ | | | |
+ | | | compr_start() |
+ | | | |
+ | | v |
+ | +----------+ +----------+ |
+ | | | compr_drain() | | compr_stop() |
+ | | DRAIN |<-------------------| RUNNING |--------------------------+
+ | | | | | |
+ | +----------+ +----------+ |
+ | | ^ |
+ | A | | |
+ | | compr_pause() | | compr_resume() |
+ | | | | |
+ | v v | |
+ | +----------+ +----------+ |
+ | | | | | compr_stop() |
+ +--->| FREE | | PAUSE |---------------------------+
+ | | | |
+ +----------+ +----------+
+
Gapless Playback
================
Line containing compr_free (between SETUP and FREE) seems to be misaligned?
If you move prepare to the left and drain in place of drain, it feels
like you won't need this weird indirection with A
Something like:
>> + v
+ compr_free() +----------+
+ +------------------------------------| |
+ | | SETUP |
+ | +------------------------>| |<-------------------------+
+ | | compr_write() +----------+ |
+ | | ^ |
+ | | | compr_drain_notify() or |
+ | | | compr_stop() |
+ | | | |
+ | | | |
+ | | +----------+ |
+ | | | | |
+ | | | DRAIN | |
+ | | | | |
+ | | +----------+ |
+ | | ^ |
+ | | | |
+ | | | compr_drain() |
+ | | | |
+ | | | |
+ | +----------+ +----------+ |
+ | | | compr_start() | | compr_stop() |
+ | | PREPARE |------------------->| RUNNING |--------------------------+
+ | | | | | |
+ | +----------+ +----------+ |
+ | | | ^ |
+ | | compr_free() | | |
+ | | compr_pause() | | compr_resume() |
+ | | | | |
+ | v v | |
+ | +----------+ +----------+ |
+ | | | | | compr_stop() |
+ +--->| FREE | | PAUSE |---------------------------+
+ | | | |
+ +----------+ +----------+
+
but this makes me question PREPARE state, how do you enter it?