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

[ibrahim]

hi,

i hope it is appropriate to send this kind of an e-mail to ffmpeg-user
list. i'd like to ask your opinions for a proposal of long term video
preservation strategy. FFV1+lpcm+mkv is a perfect solution that meets
most of the preservation requirements for video and i would recommend
that as the first option but i am also working on an additional strategy
based on keeping the video as image sequence+audio, which would make the
video part independent of video codecs and the multimedia containers.
So, there would be no extra dedicated plan for preservation of videos in
a collection but "frames" of videos would be preserved along with other
still images (like photos) and the audio part would be preserved along
with other audio works in a collection, according to the existing
preservation strategy of those media. i am posting this to ffmpeg user
list since I believe ffmpeg is the best platform to carry such activity
of having control over the process of transcoding a video to image
sequence + audio but any recommendation to post this to another list as
well is also welcome.

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.  I know that no
such image format exists. png is my best option but:
-png is up to 8bpc (besides alpha) RGB. 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? The
file size is not a constraint but being a free/libre format is...
-can PNG handle original interlacing? If one exports a png image
sequence from an interlaced video using ffmpeg, can it be later imported
back as an interlaced image sequence preserving original interlacing? If
PNG cannot handle original video interlacing, are there any other
free/libre image formats that can?
Instead of choosing one image format for all videos, is it a better
approach to choose different image formats according to the significant
properties of the videos. like one image format for interlaced source,
another image format for progressive etc...

I would appreciate any feedback


since this e-mail will be archived on the web, i'd like to state that
the content of this e-mail is free/libre and multi-licensed with all
those free cultural licenses listed at
http://freedomdefined.org/Licenses#List_of_licenses

-- 
ibrahim
GPG:F7DA A00A CFF3 9032 3E14 F8EE 1386 6EE6 29C9 E65F