Question about editing DSLR footage in Vegas.

[Frederic Baumann]

Hi,

as far as I know, Canon DSLRs encode to AVCHD, which is highly CPU-intensive to decode, so it makes Vegas and the CPU work hard while handling such files. AVCHD is highly compressed video. It can be encoded quickly (which is cool for DSLRs embedded CPUs), but the counterpart is that it requires lots of computing to decode.

For that reason, it might be better to transcode it to another format easier to process while decoding. For instance Cineform does that. I have also read that it was able to improve the quality, by making RGB channels more accurate, but I have never understood how this could be possible – the data is in the file, so if Cineform can find hidden bits, Vegas should be able to do it as well 🙂 Explanations welcome btw.

No idea about quality drop with mpeg, sorry.

Hope this helps,
Frederic

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[John Rofrano]

[Justin Leyba] ” I noticed that my computer is slower and I often get what other people call the “red screen of death”. I don’t know why this is happening because when I edit my Sony FX7 footage it works perfectly. Is the file format of the DSLR bigger than camcorders even though they both record at 1080p?”

Your FX7 shoots HDV which is very edit friendly. The T3i shoots a non-standard format of AVC/H.264 which, as Frederic said is highly compressed and very difficult to edit.

[Justin Leyba] “Anyways, I’ve been reading a couple of blogs recommending to convert DSLR native footage to mpeg streamclip. Apparently it can convert the DSLR footage into a more Vegas friendly format. Anyone ever tried it before? Will I lose quality when I convert my video?”

MPEG Streamclip is free so why don’t you download it and try it out. When you save it, choose File | Export to QuickTime… and then select the compression type. Photo-JPEG is used by a lot of stock footage houses because it retains good quality. This may or may not playback better on your system.

The three solutions that I know work are to get CineForm NeoScene ($99 USD) and convert all of your footage with that, or use VASST GearShift and convert your footage to proxies that will make editing smoother, or use Vegas Pro 10.0e which has the latest optimizations for DSLR cameras. I don’t know what version of Vegas you are using or how powerful your PC is. This could be part of the problem.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Dave Haynie]

[Frederic Baumann] “as far as I know, Canon DSLRs encode to AVCHD, which is highly CPU-intensive to decode, so it makes Vegas and the CPU work hard while handling such files. AVCHD is highly compressed video. It can be encoded quickly (which is cool for DSLRs embedded CPUs), but the counterpart is that it requires lots of computing to decode.”

Actually, AVC is very CPU intensive to encode, too. It’s just that all camcorders have dedicated AVC compression engines. The main reason for using AVC is that it has a very high encoding efficiency — when well encoded, it delivers about twice the visual of quality of MPEG-2 for the same bitrate (or the same quality at half the bitrate). Not all camcorders or HDSLRs encode AVC using all of the bells and whistles, either… and you can’t expect these devices to encode in realtime what a really fast PC might take 2x-4x realtime to accomplish.

[Frederic Baumann] “For that reason, it might be better to transcode it to another format easier to process while decoding. For instance Cineform does that. I have also read that it was able to improve the quality, by making RGB channels more accurate, but I have never understood how this could be possible – the data is in the file, so if Cineform can find hidden bits, Vegas should be able to do it as well 🙂 Explanations welcome btw.”

Ok, what you’re talking about here is color compression. Knowing that the human eye is less sensitive to color than luma, most video compression tosses out a great deal of the color. Consumer/prosumer formats are nearly always doing 4:2:0 or 4:1:1 subsampling… short explanation is that they’re tossing 3/4 of the color information. But hey, it still looks pretty good, eh?

When you convert AVCHD to Cineform, the conversion process interpolates your 4:2:0 subsampled AVC to 4:2:2 subsampled Cineform.. it’s making an intelligent guess about the “missing” color samples, but in a straight forward enough way that you don’t see anything different. And if that’s all you ever do with the video, it’s going to be ever-so-slightly lower quality than the AVC video was, thanks to the additional re-encoding process.

But when you manipulate video, there’s only so much resolution in the color. Editing in Cineform vs. AVCHD, you have in essence twice the effective color resolution… so color mathematics are just a bit less “fragile” than when operating directly on AVC.

This is similar to, though not identical to, adding guard bits in mathematical calculations, or editing a lower resolution image in Photoshop by first blowing it up a couple of times. In both cases, you’re not actually adding any usefully new information, but in duplicating and interpolating the existing information, you’re building an artificially higher resolution intermediate form, which is less subject to repeated errors in the process of manipulation.

This basic idea is also why you might do Photoshop manipulations in 16-bits/pixel, even if you’re just dealing with an 8-10-bit/pixel original, or why you pretty much always edit audio in 48-bit or floating point, even though you don’t likely have samples with more than 24-bit (if you’re lucky) actual resolution.

-Dave

[Justin L.]

Thanks guys for the info! Now I know why my Vegas is freaking out. I didn’t know I was supposed to edit my T3i footage natively in Vegas…

Quick question. If I transcode my footage to mpeg streamclip will I lose quality? Or will I only lose quality when I convert? Or is transcoding and converting the same thing?

Thanks!!

[John Rofrano]

[Justin Leyba] “Quick question. If I transcode my footage to mpeg streamclip will I lose quality?”

Yes, transcoding TO or FROM a lossy codec will always loose quality. The question is, “will it be noticeable?” and that depends on how good a codec to transcode to. This is why people who care about quality use CineForm.

[Justin Leyba] “Or will I only lose quality when I convert? Or is transcoding and converting the same thing?”

Transcoding and converting are the same thing. You may be thinking of remuxing which is just wrapering the same video in a different container but the video remains the same.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Justin L.]

Hmm interesting. I just downloaded mpeg streamclip and now I don’t know what codec to use. What codec would you recommend (best quality with a small file size). I’m debating between the Avid DNxHD codec or the H.264 codec.

[John Rofrano]

[Justin Leyba] ” I’m debating between the Avid DNxHD codec or the H.264 codec.”

H.264 is what your DSLR footage is now. Avid DNxHD would be your best choice.

~jr

http://www.johnrofrano.com
http://www.vasst.com