Received-SPF: pass (google.com: domain of linux-kernel+bounces-179724-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Message-ID: <8a6f84ac-5813-4954-b852-84f5118e607c@perex.cz>
Date: Wed, 15 May 2024 11:50:52 +0200
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v15 00/16] Add audio support in v4l2 framework
To: Hans Verkuil <hverkuil@xs4all.nl>, Shengjiu Wang
 <shengjiu.wang@gmail.com>,
 =?UTF-8?Q?Amadeusz_S=C5=82awi=C5=84ski?=
 <amadeuszx.slawinski@linux.intel.com>
Cc: 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
References: <1710834674-3285-1-git-send-email-shengjiu.wang@nxp.com>
 <20240430172752.20ffcd56@sal.lan> <ZjGhPz-bokg6ZbDJ@finisterre.sirena.org.uk>
 <87sez0k661.wl-tiwai@suse.de> <20240502095956.0a8c5b26@sal.lan>
 <20240502102643.4ee7f6c2@sal.lan> <ZjRCJ2ZcmKOIo7_p@finisterre.sirena.org.uk>
 <20240503094225.47fe4836@sal.lan>
 <CAA+D8APfM3ayXHAPadHLty52PYE9soQM6o780=mZs+R4px-AOQ@mail.gmail.com>
 <22d94c69-7e9f-4aba-ae71-50cc2e5dd8ab@xs4all.nl>
 <51408e79-646d-4d23-bc5b-cd173d363327@linux.intel.com>
 <CAA+D8AM7+SvXBi=LKRqvJkLsrYW=nkHTfFe957z2Qzm89bc48g@mail.gmail.com>
 <cd71e8e8-b4dc-40ed-935e-a84c222997e6@linux.intel.com>
 <CAA+D8AMpLB0N++_iLWLN_qettNz-gKGQz2c2yLsY8qSycibkYg@mail.gmail.com>
 <2f771fe9-7c09-4e74-9b04-de52581133fd@linux.intel.com>
 <CAA+D8AMJKPVR99jzYCR5EsbMa8P95jQrDL=4ayYMuz+Cu1d2mQ@mail.gmail.com>
 <28d423b1-49d8-4180-8394-622b1afd9cd9@perex.cz>
 <850a80b2-d952-4c14-bd0b-98cb5a5c0233@perex.cz>
 <c5dbb765-8c93-4050-84e1-c0f63b43d6c2@xs4all.nl>
From: Jaroslav Kysela <perex@perex.cz>
Content-Language: en-US
Autocrypt: addr=perex@perex.cz; keydata=
 xsFNBFvNeCsBEACUu2ZgwoGXmVFGukNPWjA68/7eMWI7AvNHpekSGv3z42Iy4DGZabs2Jtvk
 ZeWulJmMOh9ktP9rVWYKL9H54gH5LSdxjYYTQpSCPzM37nisJaksC8XCwD4yTDR+VFCtB5z/
 E7U0qujGhU5jDTne3dZpVv1QnYHlVHk4noKxLjvEQIdJWzsF6e2EMp4SLG/OXhdC9ZeNt5IU
 HQpcKgyIOUdq+44B4VCzAMniaNLKNAZkTQ6Hc0sz0jXdq+8ZpaoPEgLlt7IlztT/MUcH3ABD
 LwcFvCsuPLLmiczk6/38iIjqMtrN7/gP8nvZuvCValLyzlArtbHFH8v7qO8o/5KXX62acCZ4
 aHXaUHk7ahr15VbOsaqUIFfNxpthxYFuWDu9u0lhvEef5tDWb/FX+TOa8iSLjNoe69vMCj1F
 srZ9x2gjbqS2NgGfpQPwwoBxG0YRf6ierZK3I6A15N0RY5/KSFCQvJOX0aW8TztisbmJvX54
 GNGzWurrztj690XLp/clewmfIUS3CYFqKLErT4761BpiK5XWUB4oxYVwc+L8btk1GOCOBVsp
 4xAVD2m7M+9YKitNiYM4RtFiXwqfLk1uUTEvsaFkC1vu3C9aVDn3KQrZ9M8MBh/f2c8VcKbN
 njxs6x6tOdF5IhUc2E+janDLPZIfWDjYJ6syHadicPiATruKvwARAQABzSBKYXJvc2xhdiBL
 eXNlbGEgPHBlcmV4QHBlcmV4LmN6PsLBjgQTAQgAOBYhBF7f7LZepM3UTvmsRTCsxHw/elMJ
 BQJbzXgrAhsDBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAAoJEDCsxHw/elMJDGAP/ReIRiRw
 lSzijpsGF/AslLEljncG5tvb/xHwCxK5JawIpViwwyJss06/IAvdY5vn5AdfUfCl2J+OakaR
 VM/hdHjCYNu4bdBYZQBmEiKsPccZG2YFDRudEmiaoaJ1e8ZsiA3rSf4SiWWsbcBOYHr/unTf
 4KQsdUHzPUt8Ffi9HrAFzI2wjjiyV5yUGp3x58ZypAIMcKFtA1aDwhA6YmQ6lb8/bC0LTC6l
 cAAS1tj7YF5nFfXsodCOKK5rKf5/QOF0OCD2Gy+mGLNQnq6S+kD+ujQfOLaUHeyfcNBEBxda
 nZID7gzd65bHUMAeWttZr3m5ESrlt2SaNBddbN7NVpVa/292cuwDCLw2j+fAZbiVOYyqMSY4
 LaNqmfa0wJAv30BMKeRAovozJy62j0AnntqrvtDqqvuXgYirj2BEDxx0OhZVqlI8o5qB6rA5
 Pfp2xKRE8Fw3mASYRDNad08JDhJgsR/N5JDGbh4+6sznOA5J63TJ+vCFGM37M5WXInrZJBM3
 ABicmpClXn42zX3Gdf/GMM3SQBrIriBtB9iEHQcRG/F+kkGOY4QDi4BZxo45KraANGmCkDk0
 +xLZVfWh8YOBep+x2Sf83up5IMmIZAtYnxr77VlMYHDWjnpFnfuja+fcnkuzvvy7AHJZUO1A
 aKexwcBjfTxtlX4BiNoK+MgrjYywzsFNBFvNeCsBEACb8FXFMOw1g+IGVicWVB+9AvOLOhqI
 FMhUuDWmlsnT8B/aLxcRVUTXoNgJpt0y0SpWD3eEJOkqjHuvHfk+VhKWDsg6vlNUmF1Ttvob
 18rce0UH1s+wlE8YX8zFgODbtRx8h/BpykwnuWNTiotu9itlE83yOUbv/kHOPUz4Ul1+LoCf
 V2xXssYSEnNr+uUG6/xPnaTvKj+pC7YCl38Jd5PgxsP3omW2Pi9T3rDO6cztu6VvR9/vlQ8Z
 t0p+eeiGqQV3I+7k+S0J6TxMEHI8xmfYFcaVDlKeA5asxkqu5PDZm3Dzgb0XmFbVeakI0be8
 +mS6s0Y4ATtn/D84PQo4bvYqTsqAAJkApEbHEIHPwRyaXjI7fq5BTXfUO+++UXlBCkiH8Sle
 2a8IGI1aBzuL7G9suORQUlBCxy+0H7ugr2uku1e0S/3LhdfAQRUAQm+K7NfSljtGuL8RjXWQ
 f3B6Vs7vo+17jOU7tzviahgeRTcYBss3e264RkL62zdZyyArbVbK7uIU6utvv0eYqG9cni+o
 z7CAe7vMbb5KfNOAJ16+znlOFTieKGyFQBtByHkhh86BQNQn77aESJRQdXvo5YCGX3BuRUaQ
 zydmrgwauQTSnIhgLZPv5pphuKOmkzvlCDX+tmaCrNdNc+0geSAXNe4CqYQlSnJv6odbrQlD
 Qotm9QARAQABwsF2BBgBCAAgFiEEXt/stl6kzdRO+axFMKzEfD96UwkFAlvNeCsCGwwACgkQ
 MKzEfD96Uwlkjg/+MZVS4M/vBbIkH3byGId/MWPy13QdDzBvV0WBqfnr6n99lf7tKKp85bpB
 y7KRAPtXu+9WBzbbIe42sxmWJtDFIeT0HJxPn64l9a1btPnaILblE1mrfZYAxIOMk3UZA3PH
 uFdyhQDJbDGi3LklDhsJFTAhBZI5xMSnqhaMmWCL99OWwfyJn2omp8R+lBfAJZR31vW6wzsj
 ssOvKIbgBpV/o3oGyAofIXPYzhY+jhWgOYtiPw9bknu748K+kK3fk0OeEG6doO4leB7LuWig
 dmLZkcLlJzSE6UhEwHZ8WREOMIGJnMF51WcF0A3JUeKpYYEvSJNDEm7dRtpb0x/Y5HIfrg5/
 qAKutAYPY7ClQLu5RHv5uqshiwyfGPaiE8Coyphvd5YbOlMm3mC/DbEstHG7zA89fN9gAzsJ
 0TFL5lNz1s/fo+//ktlG9H28EHD8WOwkpibsngpvY+FKUGfJgIxpmdXVOkiORWQpndWyRIqw
 k8vz1gDNeG7HOIh46GnKIrQiUXVzAuUvM5vI9YaW3YRNTcn3pguQRt+Tl9Y6G+j+yvuLL173
 m4zRUU6DOygmpQAVYSOJvKAJ07AhQGaWAAi5msM6BcTU4YGcpW7FHr6+xaFDlRHzf1lkvavX
 WoxP1IA1DFuBMeYMzfyi4qDWjXc+C51ZaQd39EulYMh+JVaWRoY=
In-Reply-To: <c5dbb765-8c93-4050-84e1-c0f63b43d6c2@xs4all.nl>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

On 15. 05. 24 11:17, Hans Verkuil wrote:
> Hi Jaroslav,
> 
> On 5/13/24 13:56, Jaroslav Kysela wrote:
>> On 09. 05. 24 13:13, 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.
>>
>> I was thinking more about this. If I am right, the mentioned use in gstreamer
>> is supposed to run the conversion (DSP) job in "one shot" (can be handled
>> using one system call like blocking ioctl).  The goal is just to offload the
>> CPU work to the DSP (co-processor). If there are no requirements for the
>> queuing, we can implement this ioctl in the compress ALSA API easily using the
>> data management through the dma-buf API. We can eventually define a new
>> direction (enum snd_compr_direction) like SND_COMPRESS_CONVERT or so to allow
>> handle this new data scheme. The API may be extended later on real demand, of
>> course.
>>
>> Otherwise all pieces are already in the current ALSA compress API
>> (capabilities, params, enumeration). The realtime controls may be created
>> using ALSA control API.
> 
> So does this mean that Shengjiu should attempt to use this ALSA approach first?

I've not seen any argument to use v4l2 mem2mem buffer scheme for this data 
conversion forcefully. It looks like a simple job and ALSA APIs may be 
extended for this simple purpose.

Shengjiu, what are your requirements for gstreamer support? Would be a new 
blocking ioctl enough for the initial support in the compress ALSA API?

						Jaroslav

-- 
Jaroslav Kysela <perex@perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.