Den 19.02.2024 19:25, skrev Andrew Randrianasulu:
пн, 19 февр. 2024 г., 20:59 Terje J. Hanssen via Cin
<[email protected]>:
Thirty years ago I tape recordered some hundreds of old genealogy
photos, which I now plan to convert from SD-DV files to burn on
DVD video discs.
The camcordings were made with fade in/out, zoom closeups and pan
effects, which fit well at 2x playback speed and with additional
pause/play navigation on DVD videos.
Signal/noise at 2x speed with same fps and bitrate (halph of the
fps are dropped), should result in output with 1/2 playback
duration and equivalent quality as normal speed.
Yet I wonder if it possible in some way to achieve better quality
if also 2x bitrate and fps are possible to utilize temporarily as
a better quality base (downsampling), even if DVD video limits the
fps and bitrate?
They are progressive (not interlaced) dv files, right? I only can
think about fields-> frames conversion, that changes both frame size
and fps. There might be some movement interpolation algorithms, or
even neural nets nowadays, but I can't see any use of it directly in
ffmpeg (for one command conversion) as long as output remain at 25
fps. But there might be some sideefects that makes viewing better/worse?
Bitrate for consumer dv is fixed at 25Mbits, dv50 obviously goes above
that *2, but not sure if you gain anything by transcoding into dv?
(it was important when other hardware worked with those files, or they
were transferred back to tape. But our current case is single Linux
workstation only..?). mpeg2 dvd video yeah, seems to have gard upper
cap on how big bitrate-wise it can go - you can try other stuff like
custom matrixes and see if they improve quality ...
Yeah, I've tried additional "-target pal-dv50" which allowed bitrate
57Mbps, but only 25fps, which resulted in full 9 minutes duration. I
read somewhere DVCPRO50 should allow 50 fps.
By the way not so important because the conversions to .dv were merely
tests to see if 2x speed and 25fps/50fps worked.
All DV files are interlaced, while conversion "-f dvd -target pal-dvd"
creates progressive MPG(-PS) dvd video files.
What is remarkable when comparing the 4) and 5) MPG files are:
They practical have the same file size 218M, the same bitrate 6115
(6118) kb/s, the same duration 00:04:58
but different 25 fps vs 50 fps according to ffprobe.
Mediainfo reports correspondingly, and additional differences:
* Format settings, GOP : Variable vs N=15
* Bits/(Pixel*Frame) : 0.578 vs 0.289
It's not possible to see any visible difference at playback, and I will
continue with 4) due to 25 fps dvd video compliance.
I think there was yuvfps tool in mjpegtools, but I never used it ...
Here are my test samples so far:
du -sh dv95*
1) 2,0G dv95.dv (input source)
2) 1,1G dv95_2x_25fps.dv
3) 2,0G dv95_2x_50fps.dv
4) 218M dv95_2x_25fps.mpg
5) 218M dv95_2x_50fps.mpg
1)
ffprobe -hide_banner dv95.dv (source DV, Duration: 00:09:56.48)
[dv @ 0x55d65d6ca080] Estimating duration from bitrate, this
may be inaccurate
Input #0, dv, from 'dv95.dv':
Metadata:
timecode : 00:00:00:00
Duration: 00:09:56.48, start: 0.000000, bitrate: 28800 kb/s
Stream #0:0: Video: dvvideo, yuv420p, 720x576 [SAR 16:15 DAR
4:3], 28800 kb/s, 60k fps, 25 tbr, 60k tbn
Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
ffmpeg conversions using the FFmpeg setpts filter
http://trac.ffmpeg.org/wiki/How%20to%20speed%20up%20/%20slow%20down%20a%20video#setptsfilter
2)
ffmpeg -i dv95.dv -vf "setpts=0.5*PTS" -an dv95_2x_25fps.dv
ffprobe -hide_banner dv95_2x_25fps.dv
[dv @ 0x5582eb685080] Estimating duration from bitrate, this
may be inaccurate
Input #0, dv, from 'dv95_2x_25fps.dv':
Metadata:
timecode : 00:00:00:00
Duration: 00:04:58.32, start: 0.000000, bitrate: 28800 kb/s
Stream #0:0: Video: dvvideo, yuv420p, 720x576 [SAR 16:15 DAR
4:3], 28800 kb/s, 60k fps, 25 tbr, 60k tbn
3) I wonder why the Duration is still 00:09:56.52 here ?
ffmpeg -hide_banner -i dv95.dv -r 50 -vf "setpts=0.5*PTS" -an
dv95_2x_50fps.dv
ffprobe -hide_banner dv95_2x_50fps.dv
[dv @ 0x55fe0b5bb080] Estimating duration from bitrate, this
may be inaccurate
Input #0, dv, from 'dv95_2x_50fps.dv':
Metadata:
timecode : 00:00:00:00
Duration: 00:09:56.52, start: 0.000000, bitrate: 28800 kb/s
Stream #0:0: Video: dvvideo, yuv420p, 720x576 [SAR 16:15 DAR
4:3], 28800 kb/s, 60k fps, 25 tbr, 60k tbn
4)
ffmpeg -hide_banner -i dv95.dv -f dvd -target pal-dvd -aspect 4:3
-vf "setpts=0.5*PTS" -an dv95_2x_25fps.mpg
ffprobe -hide_banner dv95_2x_25fps.mpg
[mpeg @ 0x55a330208080] start time for stream 0 is not set in
estimate_timings_from_pts
Input #0, mpeg, from 'dv95_2x_25fps.mpg':
Duration: 00:04:58.32, start: 0.540000, bitrate: 6115 kb/s
Stream #0:0[0x1bf]: Data: dvd_nav_packet
Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv,
progressive), 720x576 [SAR 16:15 DAR 4:3], 25 fps, 25 tbr, 90k tbn
Side data:
cpb: bitrate max/min/avg: 9000000/0/0 buffer size: 1835008
vbv_delay: N/A
Unsupported codec with id 98312 for input stream 0
5)
ffmpeg -hide_banner -i dv95.dv -f dvd -target pal-dvd -r 50 -vf
"setpts=0.5*PTS" -an dv95_2x_50fps.mpg
ffprobe -hide_banner dv95_2x_50fps.mpg
[mpeg @ 0x555e13da2080] start time for stream 0 is not set in
estimate_timings_from_pts
Input #0, mpeg, from 'dv95_2x_50fps.mpg':
Duration: 00:04:58.26, start: 0.520000, bitrate: 6118 kb/s
Stream #0:0[0x1bf]: Data: dvd_nav_packet
Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv,
progressive), 720x576 [SAR 16:15 DAR 4:3], 50 fps, 50 tbr, 90k tbn
Side data:
cpb: bitrate max/min/avg: 9000000/0/0 buffer size: 1835008
vbv_delay: N/A
Unsupported codec with id 98312 for input stream 0
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