[FFmpeg-user] considering image sequence+audio for video preservation

Reuben Martin reuben.m at gmail.com
Mon Jun 13 06:42:58 CEST 2016

On Sunday, June 12, 2016 1:58:00 PM CDT ibrahim wrote:
> the image format for the image sequence should be a lossless compressed
> or uncompressed free/libre format and it should preserve the significant
> properties of video such as interlacing, colour space (without any
> colour conversion), chroma subsampling and bitdepth. 

That's asking a bit much. I don't think you're going to find a single solution 
that will accomidate every single scan type + color space + color sampling + 
bit-depth combination.

> I know that no
> such image format exists. png is my best option but:
> -png is up to 8bpc (besides alpha) RGB.

PNG can accomidate 16 bit (not sure if implemented in ffmpeg though).

> besides YUV to RGB colour space
> conversion, i will loose information for 10 bpc formats such as prores
> 4:2:2 when represented as 8bpc. Is there a free/libre lossless image
> format that can handle greater bitdepths? since all displays are RGB, a
> color conversion to RGB is eventually mandatory, at least when
> displaying the video/image. does anybody have a prediction that the
> display technology will switch to anything other than RGB? and my
> approach is that it would be ok to transcode to an RGB image format
> since more video codecs are expected to be RGB sometime in the future
> and the RGB image sequence can be transcoded to a RGB video format for
> access, and even for migrating to another preservation format without
> further color space conversion. what do you think? how justifiable is
> this approach? How good ffmpeg handle color space conversion for png
> image sequence? Are there any free/libre image format to preserve
> original YUV color space, original chroma subsampling and bitdepth?

For archiving in an image sequence, I would just recommend converting to a 
high bit-depth format with a linear gamma. OpenEXR is available under a 
modified BSD license and is supported by ffmpeg. It was basically designed as 
an archival interchange format. The bit-depth and dynamic range is big enough 
that no color information is ever going to get lost.


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