[Cin] Is SD and HD 422 Video Capture obtainable with V4L(2)?
Andrew Randrianasulu
randrianasulu at gmail.com
Sat Dec 18 04:35:20 CET 2021
On Saturday, December 18, 2021, Terje J. Hanssen <terjejhanssen at gmail.com>
wrote:
>
>
> 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
you missed
-intra?
ffmpeg changes cmd line and API quickly.. (
try "-g 1" and check keyframes with some linevlike those?
https://snippets.bentasker.co.uk/page-1707191206-Get-Video-Keyframe-Interval-(ffprobe)-BASH.html
> 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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