[FFmpeg-user] Capture from USB Dazzle: Interlaced or not interlaced. FFV1 level3 vs h264

Andy Furniss adf.lists at gmail.com
Thu Oct 29 21:09:21 CET 2015

Carl Eugen Hoyos wrote:
> MrNice <wxcvbn2006 <at> iol.ie> writes:
>> When I capture some video with the CL ./ffmpeg -debug 1 -f v4l2 -ts
>> mono2abs -channel 1 -video_size 720x576 -pix_fmt yuyv422
>> -thread_queue_size 512 -i /dev/video0 -c:v ffv1 -level 3 -g 1
>> -aspect 4:3 -pix_fmt yuv422p /Store3/Test/t_`date
>> +%Y%m%d_%H%M`.mkv -aspect 4:3 -f sdl "Dazzle output"
>> from a S-VHS tape and Dazzle DVC100, I was thinking to get an
>> interlaced video file.
> Why? I mean: How is FFmpeg (or the FFV1 encoder) supposed to know
> that your v4l input is interlaced?

Hopefully the device/v4l would pass on this information.

> (And why shouldn't your S-VHS recording be low-resolution
> progressive?) Maybe I miss something but in this case please
> explain.

I thought s-vhs was like vhs = one field per stripe on the tape.

Maybe if what was recorded was progressive you wouldn't care assuming
v4l outputs weaved frames - but a lot of tape contains interlaced so you
would need the field dominance info for that.

Random thought - as it's analogue field input, I wonder if it's possible
that even with a progressive recorded as interlaced you could end up
with weaved frames that don't "line up".

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