Rendering 1080 from 4K

andyrpsmith wrote on 6/7/2015, 4:01 PM

I have a ax100 and record in 4K 25p.

I render my project in Blu-Ray 24p format and have tried both mainconcept AVC and Sony AVC with varying bit rates. The problem I see with the video is flashing/strobing, for example the white window frames on a house or white down guttering flashes/pulsates. Same on both mainconcept and Sony AVC. Is this a consequence of down sampling from 4K to HD or 25p to 24p for Blu-ray?

Any suggestions welcome.
Thanks.

Comments

musicvid10 wrote on 6/7/2015, 4:08 PM

Probably a frame rate issue, 25p->24p.
Best thing is shoot 24p.
Next best thing is to disable resample.

farss wrote on 6/7/2015, 4:37 PM

[I]"Is this a consequence of down sampling from 4K to HD or 25p to 24p for Blu-ray?"[/I]

Vegas is capable of doing a perfect job of converting 25p to 24p but that does require user intervention.

Down sampling itself always been problematic in Vegas as it lack a good low pass filter. Over the years of shooting 1080 and delivering SD on DVD I've managed to avoid the problem by always shooting 50i. The advent of 4K poses a challenge as the 4K specs offer no interlaced option.

Bob.

andyrpsmith wrote on 6/7/2015, 5:04 PM

Unfortunately the AX100 only shoots 4K in 25p for the PAL version.

I'm currently comparing the mainconcept codec with the Sony AVC. The mainconcept has slightly more options to change than the Sony. The out put is very high quality but I am trying to maximise the output as much as possible.

farss wrote on 6/7/2015, 5:33 PM

[I]" I'm currently comparing the mainconcept codec with the Sony AVC"[/I]

I wouldn't waste my time trying different codecs, the problem isn't the codec.

[I]"The out put is very high quality but I am trying to maximise the output as much as possible. "[/I]

The quality of a moving image involves unavoidable trade offs compared to the quality of a still image.

Bob.

OldSmoke wrote on 6/7/2015, 7:28 PM

Try this filter package which I normally use for HD to SD. I haven't tried it on 4K to HD but it should work. The image will be a bit softer.

Another option would be to first transcode AX100 4K files down to HD with Catalyst Browse; the XAVC-Intra files also play much better in Vegas.

andyrpsmith wrote on 6/8/2015, 2:02 PM

Comparing the mainconcept at 35Mbps and the Sony at the max 23Mbps I can see no difference in picture quality (burnt to Blu-Ray and viewed on Pioneer 50" plasma TV). The Sony renders faster and produces smaller file sizes. OldSmoke how do you activate the filter? Many thanks.

OldSmoke wrote on 6/8/2015, 2:31 PM

You must install the filter package with Sony's Preset Manager.

andyrpsmith wrote on 6/8/2015, 2:51 PM

Downloaded Preset Manager and it wants to target Soundforge pro which I do not have. How does Vegas pick it up?
Thanks.

andyrpsmith wrote on 6/8/2015, 3:04 PM

I've got it now, appears as a filter folder. Many thanks.

OldSmoke wrote on 6/8/2015, 3:06 PM

The levels fx may not be necessary.

markymarkNY wrote on 6/10/2015, 9:15 AM

Another issue I have experiencing when dealing w 4k and 24p, is to make sure the source and/ or output matches exactly - 24p to 23.997p or vice-versa will lead to artifacts. They are not the same.