[FFmpeg-devel] [PATCH 2/2] avdevice/decklink_dec: add support for receiving op47 teletext

Marton Balint cus at passwd.hu
Mon Jul 3 21:54:02 EEST 2017

On Mon, 3 Jul 2017, Aaron Levinson wrote:

> On 7/3/2017 1:06 PM, Marton Balint wrote:
>> On Mon, 3 Jul 2017, Aaron Levinson wrote:
>>>> +22, and lines 318 to 335. Line 6 is the LSB in the mask. Selected lines 
>>> which
>>>> +do not contain teletext information will be ignored. You can use the 
>>> special
>>>> + at option{all} constant to select all possible lines, or 
>>>> @option{standard} 
>>> to
>>>> +skip lines 6, 318 and 319, which are not compatible with all receivers.
>>>> +
>>>> +For SD sources ffmpeg needs to be compiled with 
>>>> @code{--enable-libzvbi}. 
>>> For HD
>>>> +sources on older (pre-4K) DeckLink card models you have to capture 
>>>> in 10 
>>> bit
>>>> +mode.
>>> Would be good to indicate that the bit mask is ignored for HD sources.
>> Actually it is not. Any HD line can contain an OP47 packet referencing 
>> any SD line, the bitmask is checked against the decoded source line 
>> number from OP47.
>>> The documentation indicates that both SD PAL and HD sources are 
>>> supported, but an examination of the changes indicates that only some 
>>> HD sources are supported.  Specifically, for HD sources to work, it 
>>> expects a width of 1920.  This would cover both 1080i and 1080p, but 
>>> it doesn't cover 720p, with is also an HD video mode.  My guess is 
>>> that the code has probably only been tested with 1080i as well, and in 
>>> that case, it would make sense to only specify 1080i in the 
>>> documentation.  Further, since the original code only supports SD PAL, 
>>> I would suspect that the latest code has only been tested using "PAL" 
>>> frame rates at 1080i, i.e. 1080i50.  If it is unclear if the code will 
>>> also work with 1080i59.94 and 1080i60, then it would be best to only 
>>> support 1080i50.
>> 1080i/p/59.94/60 should work all the same. For 720p different VANC lines 
>> might be needed. I will change the HD references to "Full HD" so it will 
>> be more clear.
> Searching for "full HD" tends to indicate that term is usually 
> associated with 1080p but not with 720p nor 1080i (for example, at 
> http://www.pcmag.com/article2/0,2817,2413044,00.asp ).  I think it would 
> be clearer to call out the specific video modes that are supported.

I disagree. Full HD is resolution, not fps. Anybody working with 
interlaced signals will know that full HD means both progressive and 
interlaced here.


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