<br><br>On Thursday, December 23, 2021, Terje J. Hanssen via Cin <<a href="mailto:cin@lists.cinelerra-gg.org">cin@lists.cinelerra-gg.org</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Background:<br>
<br>
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.<br>
<a href="http://download.das-werkstatt.com/pb/mthk/info/video/comparison_video_codecs_containers.html#lossy_vs_lossless" target="_blank">http://download.das-werkstatt.<wbr>com/pb/mthk/info/video/compari<wbr>son_video_codecs_containers.<wbr>html#lossy_vs_lossless</a><br>
<br>
* Applying no compression at all (=uncompressed<br>
<<a href="http://download.das-werkstatt.com/pb/mthk/info/video/comparison_video_codecs_containers.html#codec_uncompressed" target="_blank">http://download.das-werkstat<wbr>t.com/pb/mthk/info/video/<wbr>comparison_video_codecs_contai<wbr>ners.html#codec_uncompressed</a>>)<br>
results in:<br>
* 720 x 576 x 16 bits x 25 frames ≥ 1.159 GiB/Minute<br>
*<br>
<br>
* For YUV422, 10 bpc (10+5+5 = 20 bits per pixel), this would be:<br>
* 720 x 576 x 20 bits x 25 frames ≥ 1.448 GiB/Minute<br>
<br>
<br>
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.<br>
Therefore, you will hardly find uncompressed video in the wild, except for temporary editing use cases.<br>
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The examples below show the differences in storage space required for uncompressed, lossless and lossy video codecs:<br>
<a href="https://www.scart.be/?q=en/content/short-guide-choosing-digital-format-video-archiving-masters" target="_blank">https://www.scart.be/?q=en/con<wbr>tent/short-guide-choosing-digi<wbr>tal-format-video-archiving-<wbr>masters</a><br>
<br>
* uncompressed (e.g., v210) 10-bit -> approx. 100GB per hour of video;<br>
* lossless compression (FFV1 and JPEG 2000) 10-bit -> approx. 45-50 GB<br>
per hour of video;<br>
* lossy compression;<br>
* MPEG 2/DV50/IMX50 (50 Mbps) -> approx. 25 GB per hour of video;<br>
* to compare with<br>
* DV (DV25) -> approx. 12 GB per hour of video;<br>
* MPEG 2 (DVD quality) -> approx. 3.6 GB per hour of video.<br>
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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<br>
<br>
* mathematical lossless compression with typical intraframe FFV1/MKV<br>
for preservation (archive masters)<br>
* and/or possibly "visually lossless" compression to a lossy<br>
intraframe intermediate/mezzanine format<br>
<br>
<br>
I had no uncompressed test file available, but tried this guide to generate a simple video (only) file:<br>
Compressing and uncompressing a preservation master video file<br>
<a href="https://bits.ashleyblewer.com/blog/2018/11/08/compressing-and-uncompressing-a-preservation-master-video-file/" target="_blank">https://bits.ashleyblewer.com/<wbr>blog/2018/11/08/compressing-an<wbr>d-uncompressing-a-preservation<wbr>-master-video-file/</a><br>
<br>
ffmpeg -f lavfi -i mandelbrot=size=640x480:rate=2<wbr>5 -c:v v210 -t 5 uncompressed.mov<br>
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and next to turn it to a FFV1/MKV lossless compressed file<br>
<br>
ffmpeg -i uncompressed.mov -map 0 -dn -c:v ffv1 -level 3 -g 1 -slicecrc 1 -slices 16 -c:a copy ffv1.mkv<br>
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and if required a test to uncompress the FFV1/MKV file to uncompressed 10bit file again:<br>
<br>
ffmpeg -i ffv1.mkv -c:v v210 uncompressed-again.mov<br>
<br>
du -s *<br>
105004 uncompressed.mov<br>
22844 ffv1.mkv<br>
105004 uncompressed-again.mov</blockquote><div><br></div><div>i think there is special filter (framecrc?) in ffmpeg for checking exactness of those frames (no example off hand.. <a href="http://underpop.online.fr/f/ffmpeg/help/framecrc.htm.gz">http://underpop.online.fr/f/ffmpeg/help/framecrc.htm.gz</a> ? ) </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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In this simple case the lossless compressed ffv1.mkv size is schrinked to 22% of the uncompressed.mov file.<br>
In other practical tests I read the FFV1 file size was schrinked to 1/3 to 46% of the uncompressed video.<br>
<br>
(I tested for fun to transcode a "visual lossless" compressed ProResHQ.mov file to FFV1/MKV, but that extented the file size to 180% )<br>
<br>
I loaded the simple generated ffv1.mkv in Cinelerra, but also read about a problem in a previous thread<br>
[Cin] Single-frame step fwd/bak in viewer delayed?<br>
<a href="https://www.mail-archive.com/cin@lists.cinelerra-gg.org/msg01799.html" target="_blank">https://www.mail-archive.com/c<wbr>in@lists.cinelerra-gg.org/msg0<wbr>1799.html</a><br>
<br>
Is this problem solved?<br>
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?</blockquote><div><br></div><div>I think Andrea run into slowness/desyncro with some mkvs (unsolved) </div><div><br></div><div>ffv1 can be quite cpu intensive, so fludity during edition depends on host cpu. Also, apparently there is two-level of crc codes both in ffv1 and mkv container. May be one can disable one level of checking for faster de/compression (I will look into it) </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<br>
Terje J. H<br>
<br>
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</blockquote>