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Date: Wed, 14 Jun 2023 12:55:33 +0100
From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To: Takashi Iwai <tiwai@...e.de>
Cc: vkoul@...nel.org, broonie@...nel.org, tiwai@...e.com,
corbet@....net, alsa-devel@...a-project.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
quic_plai@...cinc.com, quic_mohs@...cinc.com
Subject: Re: [PATCH v2] ALSA: compress: allow setting codec params after next
track
Thanks Takashi for review,
On 14/06/2023 08:04, Takashi Iwai wrote:
> On Fri, 09 Jun 2023 17:04:16 +0200,
> Srinivas Kandagatla wrote:
>>
>> For gapless playback it is possible that each track can have different
>> codec profile with same decoder, for example we have WMA album,
>> we may have different tracks as WMA v9, WMA v10 and so on
>>
>> Or if DSP's like QDSP have abililty to switch decoders on single stream
>> for each track, then this call could be used to set new codec parameters.
>>
>> Existing code does not allow to change this profile while doing gapless
>> playback.
>>
>> Reuse existing SNDRV_COMPRESS_SET_PARAMS to set this new track params along
>> some additional checks to enforce proper state machine.
>>
>> With this new changes now the user can call SNDRV_COMPRESS_SET_PARAMS
>> anytime after setting next track and additional check in write should
>> also ensure that params are set before writing new data.
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> ---
>> Changes since v1/RFC:
>> - removed introduction of new IOCTL, as suggested.
>> - update the state-machine doc.
>>
>> .../sound/designs/compress-offload.rst | 52 +++++++++----------
>> sound/core/compress_offload.c | 10 ++--
>> 2 files changed, 33 insertions(+), 29 deletions(-)
>>
>> diff --git a/Documentation/sound/designs/compress-offload.rst b/Documentation/sound/designs/compress-offload.rst
>> index 935f325dbc77..205cadcabe70 100644
>> --- a/Documentation/sound/designs/compress-offload.rst
>> +++ b/Documentation/sound/designs/compress-offload.rst
>> @@ -256,32 +256,32 @@ Gapless Playback SM
>> For Gapless, we move from running state to partial drain and back, along
>> with setting of meta_data and signalling for next track ::
>>
>> -
>> - +----------+
>> - compr_drain_notify() | |
>> - +------------------------>| RUNNING |
>> - | | |
>> - | +----------+
>> - | |
>> - | |
>> - | | compr_next_track()
>> - | |
>> - | V
>> - | +----------+
>> - | | |
>> - | |NEXT_TRACK|
>> - | | |
>> - | +----------+
>> - | |
>> - | |
>> - | | compr_partial_drain()
>> - | |
>> - | V
>> - | +----------+
>> - | | |
>> - +------------------------ | PARTIAL_ |
>> - | DRAIN |
>> - +----------+
>> + +----------+
>> + compr_drain_notify() | | compr_set_params() iff next-track set.
>> + +------------------------>| RUNNING |----------------------+
>> + | | | |
>> + | +----------+ |
>> + | | |
>> + | | |
>> + | | compr_next_track() |
>> + | | V
>> + | V |
>> + | +----------+ |
>> + | | | |
>> + | |NEXT_TRACK| |
>> + | | | |
>> + | +----------+ |
>> + | | |
>> + | +----------------------------+
>> + | |
>> + | | compr_partial_drain()
>> + | |
>> + | V
>> + | +----------+
>> + | | |
>> + +------------------------ | PARTIAL_ |
>> + | DRAIN |
>> + +----------+
>>
>> Not supported
>> =============
>> diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
>> index 243acad89fd3..fe67228e74b3 100644
>> --- a/sound/core/compress_offload.c
>> +++ b/sound/core/compress_offload.c
>> @@ -294,6 +294,9 @@ static ssize_t snd_compr_write(struct file *f, const char __user *buf,
>> case SNDRV_PCM_STATE_SETUP:
>> case SNDRV_PCM_STATE_PREPARED:
>> case SNDRV_PCM_STATE_RUNNING:
>> + /* Make sure next track params are set before writing new data */
>> + if (stream->next_track)
>> + return -EPERM;
>
> Hm, does this logic correctly match with the comment above?
Yes I agree, it bit confusing and also going to break the partial drain
path.
> Also, this misses the mutex unlock.
Thinking about this again, Its not required have this check here to
start with.
Something like below works, I can send this as v3, if this looks fine.
------------------------->cut<----------------------------------
diff --git a/Documentation/sound/designs/compress-offload.rst
b/Documentation/sound/designs/compress-offload.rst
index 935f325dbc77..655624f77092 100644
--- a/Documentation/sound/designs/compress-offload.rst
+++ b/Documentation/sound/designs/compress-offload.rst
@@ -268,11 +268,12 @@ with setting of meta_data and signalling for next
track ::
| |
| V
| +----------+
- | | |
- | |NEXT_TRACK|
- | | |
- | +----------+
- | |
+ | compr_set_params() | |
+ | +-----------|NEXT_TRACK|
+ | | | |
+ | | +--+-------+
+ | | | |
+ | +--------------+ |
| |
| | compr_partial_drain()
| |
diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index 243acad89fd3..30f73097447b 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -589,7 +589,7 @@ snd_compr_set_params(struct snd_compr_stream
*stream, unsigned long arg)
struct snd_compr_params *params;
int retval;
- if (stream->runtime->state == SNDRV_PCM_STATE_OPEN) {
+ if (stream->runtime->state == SNDRV_PCM_STATE_OPEN ||
stream->next_track) {
/*
* we should allow parameter change only when stream
has been
* opened not in other cases
@@ -612,6 +612,9 @@ snd_compr_set_params(struct snd_compr_stream
*stream, unsigned long arg)
if (retval)
goto out;
+ if (stream->next_track)
+ goto out;
+
stream->metadata_set = false;
stream->next_track = false;
------------------------->cut<----------------------------------
>
>
> thanks,
>
> Takashi
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