I have Nikon's and they create H.264 encoded MOV files which are compressed at a bitrate of 24 or 25 Megabits.

It would seem to me that importing at DNxHD 36 would be a high enough resolution to import these files into AVID since its 10 or 11 mbps higher than than the source material.  I'm hoping this is the case and wanted to ask if anyone can see a flaw in my understanding of AVID's importing resolutions or encoding in general.

My hope by importing at a lower resolution is to see an improvement in disk space use, and hopefully some performance improvement as well (i.e. in multi-cam editing, and possibly faster rendering of effects or smoother playback with more complex timelines with multiple realtime effects stacked up).

Can anyone confirm that my thinking is correct and/or wise?  Would I be losing anything by going from 115 to 36 if the source is 25?  It seems like I could capture a VHS tape at 115 or 36 and it would look the same... you can't improved the quality by going above the original materials quality right?  

Or is there more going on here that I don't know about?

- John

It's not that simple numerically.

H264 is a long GOP codec.

DNxHD codecs are not LONG GOP material, the same bit rate to result in inferior image.

Codec DNxHD 36 for offline HD resolution, and so can facilitate multicam.

But online you need to use higher DNxHD codec (120 and higher).

V.

One of the places I work at had this same question.  They had an 8 episode series that shot nearly 100 hours of gopro material that was mixed in with C300.  They ran several tests and concluded that there was no point in transcoding the material to anything higher than pro res proxy (FCP7 edit).  PR Proxy is pretty much the same as DNx36.  All the shows passed QC and the color correctionists had no complaints about not being able to color correct the material properly.

That being said, to my eye I've always noticed just a bit of "smudgeyness" in H264 converted to DNx36 and PR proxy material when compared to DNx115 or it's PR 422 equivalent, but that's just me.  The head of post did his do diligence and found that the extra 35 gigs per hour of storage space wasn't worth the small trade off in quality that "might" have been perceptable.

Thanks for the feedback guys.  Perhaps you could educate me more on the subject... as I seem to have more questions now... haha!

It seems like 36 should be enough since AVID DNxHD is a short GOP which is better than Long GOP... but then maybe I don't understand the encoding process enough to speak intelligently about it.  

Isn't short GOP more accurate with less artifacts because each frame is encoded independanty ("intraframe" vs. "interframe").  If so then the DNxHD codec at 36 a being short GOP method would seem like its better than the source material (long GOP at 35) in 2 ways, not just one.  

I'm sure I'm just missing a connection or a process that explains this, but It's not adding up yet... :(  Thoughts?

Vice versa. Long GOP can be more efficient, so with Long GOP you can get a better image quality at a lower data rate compared to - say - DNxHD or ProRes.

But Long GOP is a dog in postproduction.

So, rule of thumb: when transcoding Long GOP source codecs to DNxHD or ProRes, choose a significantly higher data rate.

Ahh.  That was THE missing piece. :)  Thanks for the clarification.  It all makes sense now.  My DSLR shoots Long GOP (great for efficiency and compression) but it's not good for editing.  And DNxHD is short GOP which is more accurate and larger files needed for editing.  And the bridge to connect the two is to use larger bitrates in AVID to encode.  Right?

Right.

I will say this, despite my previous comments about how my boss decided to handle converting gopro footage, there are times where DNx36 won't cut it.

I shot an event this weekend where there was text in the shot (sponsors on a boxing ring mat) and in pro res proxy you could see aliaising halos around the text.  I re-transcoded, this time to pro res LT and the halos were gone.

As with all things, test, test, test.  I still believe that while in theory, same bit rate to same bit rate conversion can be ok and will pass QC, it's not always the most pleasing to the eye.

Hello, not sure if i'm in the right forum but I have a problem importing DSLR files into avid. I have RAW material that was shot with a Canon 70D 640x480 SD .mov's h264 (I attached a picture of the specs) For some reason Avid is bringing down the resolution of the files when being viewed through AMA. I tried transcoding to DV25, 50 tried both of the h264 codecs available in the drop down menu and acouple others and none of them seem to work. The videos look soft and with interlace lines (rough edges around shoulders and faces) and the quality looks like if I had it at half of the video resolution. This is my first time working with DSLR footage and sadly it had to be SD I know that if it was HD I could use DNxHD but since the clips are SD I don't get that option in Avid. 

 

A coworker was abel to import same footage into Finalcut 7 and he had no problems with resolution or anythingz so whats the difference. The original clips look good if I view them through quicktime. 

 

Any help would be greatly appreciated.

What's your timeline playback quality setting (near the lower-left of the timeline)?  If it's full-yellow, or yellow/green, bump it up to full-green and see how that looks.

This is the right forum, but feel free to start a new topic if your issue isn't exactly the same as the topic you're replying to - especially if it's an older topic.

It is in full green and even if I bumped it up to where the green has a 10 on it it doesn't make a difrence ofcourse if I bring it down to the yello or half and half then it looks even worst. these are the specs of the original content.

Hello,

you have a project based progressive or interlace?

From what I read on the internet is recording 640 x 480 at 25p or 29.97p. (78 megabytes / min. With IPB compression.)

V.

 

GalvanAle:

640x480 SD

Since MC does not allow for custom canvas size (like FCP), importing these files will mean scaling to NTSC which is 720x480 (or 486) non-square. That scaling probably is where the ugliness comes from.

That bieng taken into consideration what would be the work around? because even though I have check the import setting of "Do not Resize smaller images" that should keep whatever size the video is to it's native size. I have done this in the past and it keep the size good or does this mean that Avid can't edit h264 Sd files from a DSLR?