[FFmpeg-devel] [PATCH 3/8] decklink: Introduce support for capture of multiple audio streams

Devin Heitmueller dheitmueller at ltnglobal.com
Fri Jan 5 22:18:18 EET 2018

Hello Matthias,

Thanks for the feedback.  Comments inline:

> On Jan 2, 2018, at 4:52 AM, Matthias Hunstock <atze at fem.tu-ilmenau.de> wrote:
> Am 29.12.2017 um 19:12 schrieb Devin Heitmueller:
>> To support the existing use case where multi-channel audio can be
>> captured (i.e. 7.1)
> Just to be clear, the current use case is NOT to capture multi-channel
> audio like 7.1. It's just to capture all of the mono SDI channels into
> one FFmpeg-internal audio stream and FFmpeg calls 8 channels "7.1”.

Right.  The existing capture module can capture 2, 8, or 16 mono channels IIRC, and they’re all bundled as a single stream.  The underlying channel map is unspecified and has to be tweaked through a filter if needed.
> As you already noticed, the audio mapping is far from standardized and
> has to be adapted anyway in most use cases... having said that, I find
> the option value "discrete" misleading. I would expect every channel to
> be in a separate stream when reading that, but I'm not a native english
> speaker. What about e.g. "bundled”?

No objection here.  The term “discrete” is just what the broadcast industry uses when sending uncompressed multi-channel audio over SDI (e.g. when dealing with 5.1 or 7.1).  That said, even in the “pairs” model I’m introducing it’s entirely possible that some of those pairs will be components to a 5.1, so I have no objection to using the vague term “bundled” since it boils down to all the possible audio channels available from the card.

> Last but not least, I cannot find an update to the documentation in this
> patch ;)

Yup, that is indeed needed.  Will include in next patch.


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