From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
To: "Jaroslav Kysela" <perex@perex.cz>,
"Shengjiu Wang" <shengjiu.wang@gmail.com>,
"Amadeusz Sławiński" <amadeuszx.slawinski@linux.intel.com>
Cc: Hans Verkuil <hverkuil@xs4all.nl>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Mark Brown <broonie@kernel.org>, Takashi Iwai <tiwai@suse.de>,
Sebastian Fricke <sebastian.fricke@collabora.com>,
Shengjiu Wang <shengjiu.wang@nxp.com>,
sakari.ailus@iki.fi, tfiga@chromium.org,
m.szyprowski@samsung.com, linux-media@vger.kernel.org,
linux-kernel@vger.kernel.org, Xiubo.Lee@gmail.com,
festevam@gmail.com, nicoleotsuka@gmail.com, lgirdwood@gmail.com,
tiwai@suse.com, alsa-devel@alsa-project.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v15 00/16] Add audio support in v4l2 framework
Date: Wed, 15 May 2024 09:04:41 -0500 [thread overview]
Message-ID: <4170720a-f7bb-484e-9235-a8720cec92c1@linux.intel.com> (raw)
In-Reply-To: <28d423b1-49d8-4180-8394-622b1afd9cd9@perex.cz>
On 5/9/24 06:13, Jaroslav Kysela wrote:
> On 09. 05. 24 12:44, Shengjiu Wang wrote:
>>>> mem2mem is just like the decoder in the compress pipeline. which is
>>>> one of the components in the pipeline.
>>>
>>> I was thinking of loopback with endpoints using compress streams,
>>> without physical endpoint, something like:
>>>
>>> compress playback (to feed data from userspace) -> DSP (processing) ->
>>> compress capture (send data back to userspace)
>>>
>>> Unless I'm missing something, you should be able to process data as fast
>>> as you can feed it and consume it in such case.
>>>
>>
>> Actually in the beginning I tried this, but it did not work well.
>> ALSA needs time control for playback and capture, playback and capture
>> needs to synchronize. Usually the playback and capture pipeline is
>> independent in ALSA design, but in this case, the playback and capture
>> should synchronize, they are not independent.
>
> The core compress API core no strict timing constraints. You can
> eventually0 have two half-duplex compress devices, if you like to have
> really independent mechanism. If something is missing in API, you can
> extend this API (like to inform the user space that it's a
> producer/consumer processing without any relation to the real time). I
> like this idea.
The compress API was never intended to be used this way. It was meant to
send compressed data to a DSP for rendering, and keep the host processor
in a low-power state while the DSP local buffer was drained. There was
no intent to do a loop back to the host, because that keeps the host in
a high-power state and probably negates the power savings due to a DSP.
The other problem with the loopback is that the compress stuff is
usually a "Front-End" in ASoC/DPCM parlance, and we don't have a good
way to do a loopback between Front-Ends. The entire framework is based
on FEs being connected to BEs.
One problem that I can see for ASRC is that it's not clear when the data
will be completely processed on the "capture" stream when you stop the
"playback" stream. There's a non-zero risk of having a truncated output
or waiting for data that will never be generated.
In other words, it might be possible to reuse/extend the compress API
for a 'coprocessor' approach without any rendering to traditional
interfaces, but it's uncharted territory.
prev parent reply other threads:[~2024-05-15 14:05 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-19 7:50 [PATCH v15 00/16] Add audio support in v4l2 framework Shengjiu Wang
2024-03-19 7:50 ` [PATCH v15 01/16] media: v4l2-ctrls: add support for fraction_bits Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 02/16] ASoC: fsl_asrc: define functions for memory to memory usage Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 03/16] ASoC: fsl_easrc: " Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 04/16] ASoC: fsl_asrc: move fsl_asrc_common.h to include/sound Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 05/16] ASoC: fsl_asrc: register m2m platform device Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 06/16] ASoC: fsl_easrc: " Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 07/16] media: uapi: Add V4L2_CAP_AUDIO_M2M capability flag Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 08/16] media: v4l2: Add audio capture and output support Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 09/16] media: uapi: Define audio sample format fourcc type Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 10/16] media: uapi: Add V4L2_CTRL_CLASS_M2M_AUDIO Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 11/16] media: uapi: Add audio rate controls support Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 12/16] media: uapi: Declare interface types for Audio Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 13/16] media: uapi: Add an entity type for audio resampler Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 14/16] media: vivid: add fixed point test controls Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 15/16] media: imx-asrc: Add memory to memory driver Shengjiu Wang
2024-03-19 7:51 ` [PATCH v15 16/16] media: vim2m-audio: add virtual driver for audio memory to memory Shengjiu Wang
2024-04-30 8:21 ` [PATCH v15 00/16] Add audio support in v4l2 framework Sebastian Fricke
2024-04-30 8:47 ` Hans Verkuil
2024-04-30 13:52 ` Mauro Carvalho Chehab
2024-04-30 14:46 ` Mark Brown
2024-04-30 15:03 ` Jaroslav Kysela
2024-04-30 16:27 ` Mauro Carvalho Chehab
2024-05-01 1:56 ` Mark Brown
2024-05-02 7:46 ` Takashi Iwai
2024-05-02 8:59 ` Mauro Carvalho Chehab
2024-05-02 9:26 ` Mauro Carvalho Chehab
2024-05-03 1:47 ` Mark Brown
2024-05-03 8:42 ` Mauro Carvalho Chehab
2024-05-06 8:49 ` Shengjiu Wang
2024-05-06 9:42 ` Jaroslav Kysela
2024-05-08 8:00 ` Hans Verkuil
2024-05-08 8:13 ` Amadeusz Sławiński
2024-05-09 9:36 ` Shengjiu Wang
2024-05-09 9:50 ` Amadeusz Sławiński
2024-05-09 10:12 ` Shengjiu Wang
2024-05-09 10:28 ` Amadeusz Sławiński
2024-05-09 10:44 ` Shengjiu Wang
2024-05-09 11:13 ` Jaroslav Kysela
2024-05-13 11:56 ` Jaroslav Kysela
2024-05-15 9:17 ` Hans Verkuil
2024-05-15 9:50 ` Jaroslav Kysela
2024-05-15 10:19 ` Takashi Iwai
2024-05-15 10:46 ` Jaroslav Kysela
2024-05-15 13:34 ` Shengjiu Wang
2024-05-16 14:58 ` Jaroslav Kysela
2024-05-15 20:33 ` Nicolas Dufresne
2024-05-16 14:50 ` Jaroslav Kysela
2024-05-27 7:24 ` Jaroslav Kysela
2024-05-15 14:04 ` Pierre-Louis Bossart [this message]
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