Background:
Digital video produces vast amounts of data. Take PAL-SD material (only
image, no audio), stored as YUV422 with 8-bits per component (=16-bits
per pixel) and a resolution of 720x576 pixels, for example.
http://download.das-werkstatt.com/pb/mthk/info/video/comparison_video_codecs_containers.html#lossy_vs_lossless
* Applying no compression at all (=uncompressed
<http://download.das-werkstatt.com/pb/mthk/info/video/comparison_video_codecs_containers.html#codec_uncompressed>)
results in:
* 720 x 576 x 16 bits x 25 frames ≥ 1.159 GiB/Minute
*
* For YUV422, 10 bpc (10+5+5 = 20 bits per pixel), this would be:
* 720 x 576 x 20 bits x 25 frames ≥ 1.448 GiB/Minute
So you would fit no more than 4 minutes of video on a whole 4.7 GiB DVD.
Since these values are already uncomfortable (even for 422-subsampled
PAL), imagine HD and beyond.
Therefore, you will hardly find uncompressed video in the wild, except
for temporary editing use cases.
-----------
The examples below show the differences in storage space required for
uncompressed, lossless and lossy video codecs:
https://www.scart.be/?q=en/content/short-guide-choosing-digital-format-video-archiving-masters
* uncompressed (e.g., v210) 10-bit -> approx. 100GB per hour of video;
* lossless compression (FFV1 and JPEG 2000) 10-bit -> approx. 45-50 GB
per hour of video;
* lossy compression;
* MPEG 2/DV50/IMX50 (50 Mbps) -> approx. 25 GB per hour of video;
* to compare with
* DV (DV25) -> approx. 12 GB per hour of video;
* MPEG 2 (DVD quality) -> approx. 3.6 GB per hour of video.
-------------
That is, if we manage to capture 422 uncompressed video via either an
internal capture card or via an external SSD recorder, there is a need for
* mathematical lossless compression with typical intraframe FFV1/MKV
for preservation (archive masters)
* and/or possibly "visually lossless" compression to a lossy
intraframe intermediate/mezzanine format
I had no uncompressed test file available, but tried this guide to
generate a simple video (only) file:
Compressing and uncompressing a preservation master video file
https://bits.ashleyblewer.com/blog/2018/11/08/compressing-and-uncompressing-a-preservation-master-video-file/
ffmpeg -f lavfi -i mandelbrot=size=640x480:rate=25 -c:v v210 -t 5
uncompressed.mov
and next to turn it to a FFV1/MKV lossless compressed file
ffmpeg -i uncompressed.mov -map 0 -dn -c:v ffv1 -level 3 -g 1 -slicecrc
1 -slices 16 -c:a copy ffv1.mkv
and if required a test to uncompress the FFV1/MKV file to uncompressed
10bit file again:
ffmpeg -i ffv1.mkv -c:v v210 uncompressed-again.mov
du -s *
105004 uncompressed.mov
22844 ffv1.mkv
105004 uncompressed-again.mov
In this simple case the lossless compressed ffv1.mkv size is schrinked
to 22% of the uncompressed.mov file.
In other practical tests I read the FFV1 file size was schrinked to 1/3
to 46% of the uncompressed video.
(I tested for fun to transcode a "visual lossless" compressed
ProResHQ.mov file to FFV1/MKV, but that extented the file size to 180% )
I loaded the simple generated ffv1.mkv in Cinelerra, but also read about
a problem in a previous thread
[Cin] Single-frame step fwd/bak in viewer delayed?
https://www.mail-archive.com/cin@lists.cinelerra-gg.org/msg01799.html
Is this problem solved?
And will the lossless compressed (preservation) format FFV1.MKV work as
a editing format, or will there be a need beside to have another
intermediate format MPEG 2/DV50/IMX50 (50 Mbps) for editing?
----------
Terje J. H
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