Re: [FFmpeg-devel] [PATCH] decklink: Add support for compressed AC-3 output over SDI

From: Devin Heitmueller <devin.heitmueller@ltnglobal.com>
To: Nicolas Gaullier <nicolas.gaullier@cji.paris>
Cc: Devin Heitmueller <dheitmueller@ltnglobal.com>,
	FFmpeg development discussions and patches
	<ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] decklink: Add support for compressed AC-3 output over SDI
Date: Fri, 10 Mar 2023 09:36:43 -0500
Message-ID: <CAHGibzGV3sRzpE-GtrsHpjE=nK=ZoEWrOhEhZOh-C2V_UjTMEQ@mail.gmail.com> (raw)
In-Reply-To: <MR1P264MB24836968AD8C18327D180C729BBA9@MR1P264MB2483.FRAP264.PROD.OUTLOOK.COM>

On Fri, Mar 10, 2023 at 2:44 AM Nicolas Gaullier
<nicolas.gaullier@cji.paris> wrote:
>
> >+static int create_s337_payload(AVPacket *pkt, enum AVCodecID codec_id,
> >+uint8_t **outbuf, int *outsize) {
>
> This is very interesting in many other contexts.
> My current patch serie is about demuxing s337 (targeting dolby_e) from wav files, and it would be great
> to be able to re-mux back to s337 in output formats, be it decklink, wav or any broadcast format.
> So, maybe this belongs to s337m.c ? It could be later updated to support dolby_e.

Hi Nicolas,

I've been following your work on s337 for a while now, as I have
corresponding patches to decklink capture and it might be better to
reuse your s337 avformat module from within the decklink libavdevice
(i.e. as a sub-demuxer).

At this point I'm inclined to keep the code separate/private to
decklink.  It's limited to AC-3 and only produces packets which are
s16 little endian.  At some point I think it would be worthwhile to
have some common code that supports 20/24 bit, both endians, and other
codecs like Dolby-E, but my concern was at this point that would
require a bunch of extra testing (much of which I don't have the
streams or hardware to do), and I didn't want to lock us permanently
into an ABI that I didn't know would meet our needs long term.

Moving it from a static function to something that can be shared is a
relatively simple operation, but I want to wait until we have a second
use case prior to refactoring the code.

Regards,

Devin

-- 
Devin Heitmueller, Senior Software Engineer
LTN Global Communications
o: +1 (301) 363-1001
w: https://ltnglobal.com  e: devin.heitmueller@ltnglobal.com
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