Encoding to H.264 from DNxHD with Squeeze 7

[Ronn Kilby]

I just export an h.264 file from Quictime Pro. Much better than Squeeze.

[Job Ter burg]

QT Pro and H264 will give you a very severe gamma shift.

[Ronn Kilby]

Sorry Job – have to disagree. I do it every day with no shift. I’d be glad to send you some samples.

[Job Ter burg]

Then you must be the only one in the world not suffering from issues with Apple’s H264 codec.

[Ronn Kilby]

Perhaps I am (or was that sarcasm? Ouch. Send an email address to H264@kilby.tv and I’ll send you a link to download “before and after” of the same clip. Then you can decide.

[Ronn Kilby]

Here ya go Job:
https://www.yousendit.com/sharedFolder?phi_action=app/orchestrateSharedFolder&id=_6RnMb8p6E4m5nPEiuhk3aQUQ7_0lA9cPFr8kwlzCSU

The DNxHD file was exported from Media Composer then loaded into QT Pro. The H.264 file was exported from there. I do this every day for dozens of TV stations and never one complaint. I have also done this with long form work (a 96 minute feature film) with no gamma shifts, no audio “slipping.”

Comments welcome.

[Job Ter burg]

Ronn, yes, sorry about the sarcasm.

Your examples, however, do show a gamma shift.

Your DNxHD appears to have been exported with stretched levels, so it runs 0-255 (not broadcast legal). The H264 appears to be broadcast legal. Rescaling one of them (I corrected the DNxHD back to 16-235), and comparing two frames shows quite a different gamma, most notably in the details in the sky of the H264. (BTW, I’m using AMA to link to your files, and use Source Settings to compensate the DNxHD back to 16-235).

But even at desktop level, the very first frame of your spot demonstrates the issue. The symbol above the World Cup logo looks fine in DNxHD, but is only half visible in the H264 (where it blends to full white with the ‘hot’ sky).

The issues with QT and some codecs (ProRes, H264) have been popping up everywhere on forums like these over the past few years.

I haven’t managed to export to H264 without any gamma shifts, but there was much less of a shift when using the Main Concept H264 encoder that is featured in Squeeze.

IMO, the best way to export a file for broadcast, with correct levels, is to avoid QrapTime, and export as Op1A MXF (Export to a virtual XDCAM device).

[Job Ter burg]

Screengrabs from the QT’s you sent:

https://www.jobterburg.nl/EVEN/RonnDNxHD.png
https://www.jobterburg.nl/EVEN/RonnH264.png

And WFM grabs:

https://www.jobterburg.nl/EVEN/WFM_DNxHD_Unmodified.png
https://www.jobterburg.nl/EVEN/WFM_DNxHD_Modified.png
https://www.jobterburg.nl/EVEN/WFM_H264_Unmodified.png

[Job Ter burg]

My favorite test chart by the way:

https://www.belle-nuit.com/testchart.html

Import this into your Avid without modifying levels (choose 709), and you will have a great test chart with legal and illegal levels. Nice one to carry through your workflow and see if you can preserve accurate levels throughout.

[Ronn Kilby]

Thanks for setting me straight, Job (no sarcasm intended) – I’ll have to return the money I’ve been paid for all those spots. (Not really). I’ll have to try out those test charts when I have some downtime – maybe next year.