Blackmagic Forum

Hi all, I hope you guys can help.

Lately our client just got back to us saying iTunes rejected the prores file we've provided to them, and the main issue is that there are consistent duplicate frames throughout the file.

For a bit of a background, client gives us 2k DPX of a movie (which are scans of old films), I then convert them to prores proxy, and give the low-res file to our sound guys together with the digitized audio the client provides so they can "clean" and up-mix it to 5.1

After the sound is approved, I go back to davinci resolve, and using the original 2k DPX, lay-in the 5.1 audio, re-frame the 2048x1556 DPX to 1998x1080 1.85 Flat, and render it out to Prores 422HQ with 6 channels of audio.

I do not know where the problem is, where the duplicate frames are coming from. I set the framerate to whatever the fps of source DPX is. So why does Baton(Interra systems QC software) say the prores has duplicate frames? Is this Resolve's fault? I've used 12.5.6 on our old renders, and even when trying it with Resolve 14.3 the problem still exists everytime they QC the files.

Check the frame rate in clip attributes and make very sure that your timeline has the same.
If they are any different, like less frames from the source than the TL setting, Resolve will silently double frames to keep up (if not set to optical flow).

Uli Plank wrote:Check the frame rate in clip attributes and make very sure that your timeline has the same.
If they are any different, like less frames from the source than the TL setting, Resolve will silently double frames to keep up (if not set to optical flow).

Thanks for responding. I always check clip attributes before importing them into resolve, I made the mistake of putting 29.97fps clips in a 23.976 timeline before and promised never to make the same mistake again.

Long story short, if the dpx is 24fps then that's what I set my timeline framerate, and the output framerate, too.

Sent from my SM-A710Y using Tapatalk

Then I'm stumped.
How does it look like of you step through your ProRes files? Which fps do they display on import?

Wait: if there are very few duplicates, could it be 23.98 vs. 24 fps?

Have you checked the DPX sequence?

Uli Plank wrote:Then I'm stumped.
How does it look like of you step through your ProRes files? Which fps do they display on import?

Wait: if there are very few duplicates, could it be 23.98 vs. 24 fps?

Hi there, sorry it took so long to reply. This is still a mystery, when i go frame by frame on the prores file i render looking for a duplicate frame there seems to be none, of course ( i wouldn't be doing it for the whole movie ) it's just that QC notes imply that there are consistent duplicate frames on our render

As I said I always check FPS, they give us 23.976, I render 23.976. So this is really weird. Any more ideas you can help me with ?

Any chance the original was transferred at 29.97 and Inverse Telecine applied to bring it back to 24fps?

If it is an older film, the original transfer could have been done to broadcast standard, and rather than pay for a new transfer, it might have been run through something like a Clipster with Inverse Telecine to electronically bring it back to 24fps.

Rayjohn Tagayon wrote:

Uli Plank wrote:Then I'm stumped.
How does it look like of you step through your ProRes files? Which fps do they display on import?

Wait: if there are very few duplicates, could it be 23.98 vs. 24 fps?

Hi there, sorry it took so long to reply. This is still a mystery, when i go frame by frame on the prores file i render looking for a duplicate frame there seems to be none, of course ( i wouldn't be doing it for the whole movie ) it's just that QC notes imply that there are consistent duplicate frames on our render

As I said I always check FPS, they give us 23.976, I render 23.976. So this is really weird. Any more ideas you can help me with ?

Baton should give you exact timecode/frame number and thumbnail(?) for those repeated frames- ask for it!
There may be in your source material- you just don't know.
When you have timecode then check with eye which in this case is the best QC tool
Those QC tools are quite crap inn reality.

When you go frame by frame you see no repeated frames? Are there any holds there- still, or black? (this is what Baton can treat as duplicate frames in theory).
There may be some MOV structural issue where Baton reads same frame many times, but if few players don't show it this way then it's Baton issue. Check on many (different) players- PC and Mac if you can.

Andrew Kolakowski wrote:

Rayjohn Tagayon wrote:

Uli Plank wrote:Then I'm stumped.
How does it look like of you step through your ProRes files? Which fps do they display on import?

Wait: if there are very few duplicates, could it be 23.98 vs. 24 fps?

Hi there, sorry it took so long to reply. This is still a mystery, when i go frame by frame on the prores file i render looking for a duplicate frame there seems to be none, of course ( i wouldn't be doing it for the whole movie ) it's just that QC notes imply that there are consistent duplicate frames on our render

As I said I always check FPS, they give us 23.976, I render 23.976. So this is really weird. Any more ideas you can help me with ?

Baton should give you exact timecode/frame number and thumbnail(?) for those repeated frames- ask for it!
There may be in your source material- you just don't know.
When you have timecode then check with eye which in this case is the best QC tool
Those QC tools are quite crap inn reality.

When you go frame by frame you see no repeated frames? Are there any holds there- still, or black? (this is what Baton can treat as duplicate frames in theory).
There may be some MOV structural issue where Baton reads same frame many times, but if few players don't show it this way then it's Baton issue. Check on many (different) players- PC and Mac if you can.

Hi, sorry i didn't put it quite clearly. The client is the one with baton (and itunes, i suppose) In our post house we only do qc by eye. If there is no stuttering or any weird things that happen in the video then it passes qc.

When I go frame by frame it looks fine to me. No repeared frames or anything. In this particular movie (dpx came from a scan of an old film) there are no holds or black frames in the editing.

Sent from my SM-A710Y using Tapatalk

Quite simple solution for me. Ask for timecodes with repeated frames.
Check by eye with 2 different players. If not there, it's Baton issue.
Don't take it as 100% correct only becasue someone said it based on Baton report.

One more important thing- make sure you are checking exactly same file as sent to client! (not eg. in Resolve project).

You can run this on your final file:
ffmpeg -i "path to source file" -filter_complex "tblend=all_mode=exclusion,blackframe=amount=100" -f null -

and if you see in output any line with:

[Parsed_blackframe_1 @ 0x7fec9bd049c0] frame:0 pblack:100....

then there are repeated frames in your file.
This checks for 100% exactly the same frames (next to each other).
Just note that if there are any black frames (1 sec. black up front/end) they will be detected as repeated also.