[FFmpeg-user] DeckLink Output Controls

Reuben Martin reuben.m at gmail.com
Tue Oct 11 08:20:02 EEST 2016

On Sunday, October 9, 2016 11:48:27 PM CDT Marcelo Boufleur wrote:
> > SDI is 20bit 48k audio only. There’s really no good reason for anything
> > else.
> > Technically SDI also supports 48048 and 47952 to allow for pull up/down,
> > but I
> > think that is done by manipulating the clock rather than explicitly
> > changing
> > the sample rate.
> SD-SDI PCM Audio is 20 bits, but it can also support 24 bits according to
> SMPTE 272M.
> Sampling rate can also range from 32Khz to 48Khz.
> For HD, there's also SMPTE 299M which mandates 24 bit audio, and also
> sampling rates range from 32Khz to 48Khz.

Although that is in the official spec, I have never seen any SDI equipment use 
anything other than 48k. Doesn’t mean any doesn’t exist, but if so it’s not 
very common.

I’m not sure there is a difference between 20 and 24 bit audio (in reguards to 
the bit allocation within the signal) since 20 bit is usually padded inside of 
a 24 or 32 bit word size. 

> You can also have 20 bit in HD (and also SD) in the form of non-audio PCM
> Data, using SMPTE 337M format (for Dolby-E and other compressed formats
> described in SMPTE 338M).

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