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 _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
