[FFmpeg-devel] [PATCH] libavdevice/decklink: 32 bit audio support

Dave Rice dave at dericed.com
Wed Oct 18 16:41:11 EEST 2017

> On Oct 17, 2017, at 3:30 PM, Douglas Marsh <ffmpeg at dx9s.net> wrote:
> On 2017-10-17 09:10, Dave Rice wrote:
>>>> -audio_depth      <int>         .D...... audio bitdepth (from 0 to 1)
>>>> (default 16bits)
>>>>    16bits                       .D......
>>> Hmm, first patch might be enough.
>> Sounds good to me. Unless anyone prefers "-audio_depth thirtytwo" :-D
>> Dave Rice
> Yeah that works.. so if they have any other depths, can go 0, 1 or 2 (2=some new bit depth yet to be created)
> And for clarification: yes 32-bits (PCM_S32LE) -- I was just pointing out the ADC/DAC's are 24-bit (8-bits padded).

I was suggesting `-audio_depth thirtytwo` in jest. IMHO assigning enumerated index numbers to purely numerical values will be confusing. For instance if in the future 12 bit is added then 24 bit, we'll have 
-audio_depth      <int>         .D...... audio bitdepth (from 0 to 3) (default 16bits)
   16bits [0]
   32bits [1]
   12bits [2]
   24bits [3]

The alternative patch in the "decklink 24/32 bit question" thread, changes the default behavior of the decklink input which I think should be avoided. I agree with Moritz that the  first patch of this thread (https://patchwork.ffmpeg.org/patch/5588/) is the best option. Also the method used in the patch to validate a limited non-consecutive range of values is already in used elsewhere in the device for the channel count at https://github.com/FFmpeg/FFmpeg/blob/278588cd0bf788df0194f74e62745f68559616f9/libavdevice/decklink_dec.cpp#L859-L868.

Best Regards,

Dave Rice

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