[FFmpeg-devel] [PATCH 1/2] avdevice/decklink: addition of copyts option

[Marton Balint]

On Sat, 20 Jan 2018, Carl Eugen Hoyos wrote:

> 2018-01-20 19:50 GMT+01:00 Marton Balint <cus at passwd.hu>:
>>
>> On Sat, 20 Jan 2018, Carl Eugen Hoyos wrote:
>>
>>> 2018-01-08 6:26 GMT+01:00  <vdixit at akamai.com>:
>>>
>>>> + at item decklink_copyts
>>>> +If set to @option{true}, timestamps are forwarded as they are without
>>>> removing
>>>> +the initial offset.
>>>> +Defaults to @option{false}.
>>>
>>>
>>> Why is the offset ever removed?
>>> I believe this is not done for any other demuxer or is it?
>>
>> The code keeps track separate audio and video initial offset
>
> But they can't be independent or can they?
> And if they can, how is A/V sync assured?

Well, I am not entirely sure. Decklink has always had problems with 
timestamps and A-V desync was not uncommon when using the default clock 
sources. Probably a bug in the SDK.

The whole offset removal is is originated from this commit:

https://github.com/lu-zero/bmdtools/commit/b51ce3841ea763f27431ed9c77b99ae5404180c6

Regards,
Marton