[Cin] Is SD and HD 422 Video Capture obtainable with V4L(2)?

[Terje J. Hanssen]

Den 19.12.2021 16:40, skrev Andrew Randrianasulu:
>
>
> On Sunday, December 19, 2021, Terje J. Hanssen 
> <terjejhanssen at gmail.com <mailto:terjejhanssen at gmail.com>> wrote:
>
>
>
>
>     Thanks, script testrun executed with attached output here.
>         Test-run_Intra-frame_key_word
>
>     As seen below from the summary table, all files except the MPEG-2
>     generated "SD-MP2-50.mpg" without the ffmpeg -intra flag set,
>     contains all Intra-frames only:
>
>     -------------------------------------------------------
>     du -sh SD*.*            # key_frame=1    # key_frame=0
>                     (# I-frames)    (# non-I-frames)
>     284M    SD-MOV.mov            746        0
>     205M    SD-DV50.dv            745        0
>     186M    SD-MP2I50.mpg            745        0
>     153M    SD-MP2I-.mpg            745        0
>     186M    SD-MP2-50.mpg             63        682
>     146M    SD-MP2I50-an.m2v        745        0
>
>
> good!
>
> but a bit concerned 746 vs 745 frame count. Are we losing one frame 
> somewhere?
>
>
To repeat:
1. SD-MOV.mov (ProRes) was the initial record source

2. SD-DV50.dv was encoded from ProRes using a simple ffmpeg target (preset)
ffmpeg -i SD-MOV.mov -target pal-dv50 SD-DV50.dv

3. The SD-MP2* were encoded from SD-DV50.dv using ffmpeg

All ffmpeg generated files has the same frame counts

My take:
The single frame difference seems to occure from step 1 -  2, or the 
script doesn't count 1 indentical as the ffmpeg generated 2 and 3.





>     Counts matched # key_frame=1 (I-frames)
>     ./kfrm.sh SD-MOV.mov | grep -c key_frame=1
>
>     Counts other (unmatched) than key_frame=1
>     ./kfrm.sh SD-MOV.mov | grep -v -c key_frame=1
>
>     --------------------------------------------------------
>

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