Optimise XDCAMHD422 Picture Quality - Syntax questions

classic Classic list List threaded Threaded
4 messages Options
Reply | Threaded
Open this post in threaded view
|

Optimise XDCAMHD422 Picture Quality - Syntax questions

Christoph Gerstbauer-2
Hello

I am using this syntax to generate a XDCAMHD422 file:

-c:v mpeg2video -r 25 -pix_fmt yuv422p -s 1920x1080 -aspect 16:9 -minrate
50000k -maxrate 50000k -b:v 50000k -g 12 -flags +ildct+ilme -intra_vlc 1
-dc 10 -non_linear_quant 1 -bf 2 -qmin 1 -qmax 12 -top 1 -bufsize 17825792
-rc_init_occupancy 17825792 -rc_min_vbv_use 1 -rc_max_vbv_use 1
-sc_threshold 1000000000 -lmin "1*QP2LAMBDA" -vtag xd5c -color_range tv
-color_primaries bt709 -color_trc bt709 -c:a pcm_s24le -ar 48000 -f mxf
-timecode 12:34:56:11 -max_muxing_queue_size 1024 -metadata
"creation_time=2015-10-28T15:37:56"

I mentioned by checking frame by frame with an editing tool (after effects)
that there are some frame with very much blockingess.
I tried with qmin/qman different values and surprisingly when using qmin=4
then the quality gets better.

With qmin4 there are still tiny blocks (looks better than qmin=1), and I
now from other transcoders that the frames were these tiny blocks happen
CAN BE better encoded so that no blocks are visible for the whole GOP.
My questions are:
1.) Why do I get a better quality with qmin=4 instead of qmin=1? -> Maybe
is datarate saved with qmin=4 which can be used for other frames were it is
needed more?
2.) How can I improve the encoding a little bit more here in ffmpeg
regarding the picture quality?

br
Christoph
_______________________________________________
ffmpeg-user mailing list
[hidden email]
http://ffmpeg.org/mailman/listinfo/ffmpeg-user

To unsubscribe, visit link above, or email
[hidden email] with subject "unsubscribe".
Reply | Threaded
Open this post in threaded view
|

Re: Optimise XDCAMHD422 Picture Quality - Syntax questions

Frédéric Busnel-Joncour

> […]
>
> With qmin4 there are still tiny blocks (looks better than qmin=1), and I
> now from other transcoders that the frames were these tiny blocks happen
> CAN BE better encoded so that no blocks are visible for the whole GOP.
> My questions are:
> 1.) Why do I get a better quality with qmin=4 instead of qmin=1? -> Maybe
> is datarate saved with qmin=4 which can be used for other frames were it is
> needed more?
> 2.) How can I improve the encoding a little bit more here in ffmpeg
> regarding the picture quality?
>

Hi there,


These are very interesting questions !
I can't explain the first point, but probably 2-pass encoding can improve encoding the way you want.
If an expert can confirm and give a command line example, that would be perfect.


Best,

Fred

_______________________________________________
ffmpeg-user mailing list
[hidden email]
http://ffmpeg.org/mailman/listinfo/ffmpeg-user

To unsubscribe, visit link above, or email
[hidden email] with subject "unsubscribe".
Reply | Threaded
Open this post in threaded view
|

Re: Optimise XDCAMHD422 Picture Quality - Syntax questions

Marton Balint
In reply to this post by Christoph Gerstbauer-2


On Tue, 23 Oct 2018, Chris von Görstinger wrote:

> Hello
>
> I am using this syntax to generate a XDCAMHD422 file:
>
> -c:v mpeg2video -r 25 -pix_fmt yuv422p -s 1920x1080 -aspect 16:9 -minrate
> 50000k -maxrate 50000k -b:v 50000k -g 12 -flags +ildct+ilme -intra_vlc 1
> -dc 10 -non_linear_quant 1 -bf 2 -qmin 1 -qmax 12 -top 1 -bufsize 17825792
> -rc_init_occupancy 17825792 -rc_min_vbv_use 1 -rc_max_vbv_use 1
> -sc_threshold 1000000000 -lmin "1*QP2LAMBDA" -vtag xd5c -color_range tv
> -color_primaries bt709 -color_trc bt709 -c:a pcm_s24le -ar 48000 -f mxf
> -timecode 12:34:56:11 -max_muxing_queue_size 1024 -metadata
> "creation_time=2015-10-28T15:37:56"
>
> I mentioned by checking frame by frame with an editing tool (after effects)
> that there are some frame with very much blockingess.
> I tried with qmin/qman different values and surprisingly when using qmin=4
> then the quality gets better.
>
> With qmin4 there are still tiny blocks (looks better than qmin=1), and I
> now from other transcoders that the frames were these tiny blocks happen
> CAN BE better encoded so that no blocks are visible for the whole GOP.
> My questions are:
> 1.) Why do I get a better quality with qmin=4 instead of qmin=1? -> Maybe
> is datarate saved with qmin=4 which can be used for other frames were it is
> needed more?

That would be my guess too.

> 2.) How can I improve the encoding a little bit more here in ffmpeg
> regarding the picture quality?

You can try using -mbd bits, it's going to be significantly slower, but in
my experience it provides better quality.

Regards,
Marton
_______________________________________________
ffmpeg-user mailing list
[hidden email]
http://ffmpeg.org/mailman/listinfo/ffmpeg-user

To unsubscribe, visit link above, or email
[hidden email] with subject "unsubscribe".
Reply | Threaded
Open this post in threaded view
|

Re: Optimise XDCAMHD422 Picture Quality - Syntax questions

Christoph Gerstbauer-2
Hello Marton,

I did use mdb bits and rt. But it didnt get better in my opinion. Maybe I
am too sensible for blocking artefacts.
mdb is my last option to improve the mpeg2 encoding. Right?


Am Di., 23. Okt. 2018 um 13:38 Uhr schrieb Marton Balint <[hidden email]>:

>
>
> On Tue, 23 Oct 2018, Chris von Görstinger wrote:
>
> > Hello
> >
> > I am using this syntax to generate a XDCAMHD422 file:
> >
> > -c:v mpeg2video -r 25 -pix_fmt yuv422p -s 1920x1080 -aspect 16:9 -minrate
> > 50000k -maxrate 50000k -b:v 50000k -g 12 -flags +ildct+ilme -intra_vlc 1
> > -dc 10 -non_linear_quant 1 -bf 2 -qmin 1 -qmax 12 -top 1 -bufsize
> 17825792
> > -rc_init_occupancy 17825792 -rc_min_vbv_use 1 -rc_max_vbv_use 1
> > -sc_threshold 1000000000 -lmin "1*QP2LAMBDA" -vtag xd5c -color_range tv
> > -color_primaries bt709 -color_trc bt709 -c:a pcm_s24le -ar 48000 -f mxf
> > -timecode 12:34:56:11 -max_muxing_queue_size 1024 -metadata
> > "creation_time=2015-10-28T15:37:56"
> >
> > I mentioned by checking frame by frame with an editing tool (after
> effects)
> > that there are some frame with very much blockingess.
> > I tried with qmin/qman different values and surprisingly when using
> qmin=4
> > then the quality gets better.
> >
> > With qmin4 there are still tiny blocks (looks better than qmin=1), and I
> > now from other transcoders that the frames were these tiny blocks happen
> > CAN BE better encoded so that no blocks are visible for the whole GOP.
> > My questions are:
> > 1.) Why do I get a better quality with qmin=4 instead of qmin=1? -> Maybe
> > is datarate saved with qmin=4 which can be used for other frames were it
> is
> > needed more?
>
> That would be my guess too.
>
> > 2.) How can I improve the encoding a little bit more here in ffmpeg
> > regarding the picture quality?
>
> You can try using -mbd bits, it's going to be significantly slower, but in
> my experience it provides better quality.
>
> Regards,
> Marton
> _______________________________________________
> ffmpeg-user mailing list
> [hidden email]
> http://ffmpeg.org/mailman/listinfo/ffmpeg-user
>
> To unsubscribe, visit link above, or email
> [hidden email] with subject "unsubscribe".



--
--------------------------------------------------------------------------------------------------------
Student der Fachhochschule für Telekommunikation und Medien St. Pölten
Student of the university of applied sciences St. Pölten

Christoph Gerstbauer
St. Paul-Gasse 6/4
A-3500 Krems an der Donau
phone:  +43 (0) 699 - 11 658 238
email:    [hidden email]
[hidden email]
[hidden email]
ICQ: 292233201
_______________________________________________
ffmpeg-user mailing list
[hidden email]
http://ffmpeg.org/mailman/listinfo/ffmpeg-user

To unsubscribe, visit link above, or email
[hidden email] with subject "unsubscribe".