[Cin] Is SD and HD 422 Video Capture obtainable with V4L(2)?
Terje J. Hanssen
terjejhanssen at gmail.com
Sat Dec 18 00:10:23 CET 2021
Den 17.12.2021 22:49, skrev Andrew Randrianasulu:
>
>
> On Saturday, December 18, 2021, Terje J. Hanssen via Cin
> <cin at lists.cinelerra-gg.org <mailto:cin at lists.cinelerra-gg.org>> wrote:
>
>
>
> Den 17.12.2021 15:00, skrev Terje J. Hanssen:
>
>
> Den 17.12.2021 04:58, skrev Andrew Randrianasulu:
>
>
>
> On Friday, December 17, 2021, Terje J. Hanssen
> <terjejhanssen at gmail.com <mailto:terjejhanssen at gmail.com>
> <mailto:terjejhanssen at gmail.com
> <mailto:terjejhanssen at gmail.com>>> wrote:
>
> [......]
>
> ===============
>
> I-frame-only 50 Megabit MPEG-2 or comparable DV50 in
> 4:2:2 as
> high-end, "visually lossless" intermediate format for
> archival and
> suited for editing?
>
> -----------------
>
> Regarding DV50, FFMpeg has a friendly "target dv50"
> support
> (similar as "target DVD"). So to get a first look on a
> DV50 test
> file, I simply transcoded 422/10bit Video and PCM
> audio from a MOV
> file (ProRes 422HQ) to a raw DV50 (422/8bit) file:
>
> ffmpeg -i SD-MOV.mov -target pal-dv50 SD-DV50.dv
>
> [......]
>
>
> 205M SD-DV50.dv (ffmpeg re-encoded/remuxed) AV-info:
>
> avprobe SD-DV50.dv
> avprobe version 12.3, Copyright (c) 2007-2018 the
> Libav developers
> built on Mar 26 2018 12:39 with gcc 11 (SUSE Linux)
> [dv @ 0x55cdddb96440] Estimating duration from
> bitrate, this may
> be inaccurate
> Input #0, dv, from 'SD-DV50.dv':
> Metadata:
> timecode : 00:00:00:00
> Duration: 00:00:29.80, start: 0.000000, bitrate:
> 57600 kb/s
> Stream #0:0: Video: dvvideo, yuv422p, 720x576 [SAR
> 16:15 DAR
> 4:3], 25000 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
> Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo,
> s16, 1536 kb/s
> Stream #0:2: Audio: pcm_s16le, 48000 Hz, stereo,
> s16, 1536 kb/s
> # avprobe output
>
> ===================
>
> As seen above, it looks like ffmpeg produced wrong
> meta data for
> the DV50 video bitrate (25 Mb/s=DV25), while the total
> bitrate
> 57.6 Mb/s is correct. (Also similar was seen with
> ffprobe and
> Mediainfo).
>
> My VLC player or Gnome movieplayer did not playback
> the DV50 file,
> while ffplay did (as usual without audio?).
>
> Cin-GG miss a DV50 preset among format setting.
> However DV50 else
> loades preliminary OK in Cin-GG (via ffmpeg).
>
>
> I'll look at dv50 output preset..
>
> Fine
>
> ===============
>
> I tried also to transcode and remux 422 Video and PCM Audio to a
> 50 Mbps MPEG-2 I-frame only program stream.
>
> 1) MPG From MOV (ProRes 422HQ)
> ------------------------------
>
> ffmpeg -i SD-MOV.mov -c:v mpeg2video -bf 2 -b:v 50M -maxrate 50M
> -minrate 50M -c:a pcm_s16be -f vob SD-MP2I-50.mpg
> [....]
> Stream mapping:
> Stream #0:0 -> #0:0 (prores (native) -> mpeg2video (native))
> Stream #0:1 -> #0:1 (pcm_s24le (native) -> pcm_s16be (native))
> Press [q] to stop, [?] for help
> [mpeg2video @ 0x560ffd164ec0] Automatically choosing VBV buffer
> size of 746 kbyte
> [vob @ 0x560ffd14d180] At most 8 channels allowed for LPCM streams.
> Could not write header for output file #0 (incorrect codec
> parameters ?): Invalid argument
> Error initializing output stream 0:1 --
>
> ***This failed because PreRes Audio uses 16 channels:***
>
>
> yeah... interesting limitation.. and interesting number of channels..
>
>
> ffprobe SD-MOV.mov 2>&1 >/dev/null | grep Stream.*Audio
> Stream #0:1(eng): Audio: pcm_s24le (lpcm / 0x6D63706C), 48000
> Hz, 16 channels, s32 (24 bit), 18432 kb/s (default)
>
>
> 2) MPG from DV50
> ----------------
> ffmpeg -i SD-DV50.dv -c:v mpeg2video -bf 2 -b:v 50M -maxrate 50M
> -minrate 50M -c:a pcm_s16be -f vob SD-MP2I-50.mpg
>
> du -sh *
> 205M SD-DV50.dv
> 284M SD-MOV.mov
> 186M SD-MP2I-50.mpg
>
> avprobe SD-MP2I-50.mpg
> Input #0, mpeg, from 'SD-MP2I-50.mpg':
> Duration: 00:00:29.77, start: 0.540000, bitrate: 52167 kb/s
> Stream #0:0[0x1e0]: Video: mpeg2video (4:2:2), yuv422p(tv,
> progressive), 720x576 [SAR 16:15 DAR 4:3], 50000 kb/s, 25 fps, 25
> tbr, 90k tbn, 50 tbc
> Stream #0:1[0xa0]: Audio: pcm_dvd, 48000 Hz, 2 channels, s16,
> 1536 kb/s
>
> ***** The SD-MP2I-50.mpg file size is here 90% of DV50 ********
>
> The SD-MP2I-50.mpg playback ok with VLC, Gnome movieplayer,
> ffplay, and loads and playback in Cin-GG
> The audio volume seems low (weak), but can probably be adjusted
> higher with ffmpeg
>
>
> well, but I missed keyframe parameter? bitrate is big but I think
> without special param ffmpeg still will not make all-I mpeg2 stream..?
>
>
The first Video part of my ffmpeg script was based on this standard
FFmpeg Howto for
"MPEG-2 I-frame only Highest Quality Encoding", which didn't include a
keyframe parameter !?
https://brunosan.eu/images/ffmpeg_howto.html#Encoding_MPEG-2_I-frame_only_in_Highest_Quality
ffmpeg -i <input_file> -vcodec mpeg2video -pix_fmt yuv422p -qscale 1
-qmin 1 -intra -an output.m2v
I dropped -pix_fmt yuv422p when I saw it was detected and automatic from
the input file.
So I added the second PCM Audio part (similar I did for SD-DV) according
to 1. Answer at
https://stackoverflow.com/questions/48265448/mpeg-2-program-stream-w-pcm-audio
FFmpeg only supports muxing 16 bit PCM in a MPEG2 PS. Use
ffmpeg -i "input.mov" \
-c:v mpeg2video -pix_fmt yuv422p -bf 2 -b:v 50M -maxrate 50M -minrate
50M \
-s 1920x1080 -aspect 16:9 \
-c:a pcm_s16be -f vob "output.mpg"
The -f vob is needed to force a MPEG-2 PS, else ffmpeg will select
MPEG-1 Systems muxer.
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