FORUMS: list search recent posts

Transcoding from Apple intermediate Codec back to HDV for archival purposes?

COW Forums : Apple Final Cut Pro Legacy

<< PREVIOUS   •   FAQ   •   VIEW ALL   •   PRINT   •   NEXT >>
will johnston
Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 14, 2011 at 12:51:51 pm

Hi Everybody. i'm hoping one of the resident experts can give me some advice.

We've produced around 250 videos in the last few years, most near an hour in length. In order to make it easier (less processor intensive) to edit, we've been transcoding the raw video files to Apple Intermediate Codec files from HDV upon import. When the edits were completed, we exported the final videos using the same settings, so we currently have a library of several hundred hours of AIC video.

As you can imagine, this is taking a huge amount of hard disk space to archive, not to mention the multiple backup copies which i've been making and saving far away in case disaster strikes.

im currently considering to transcode all the AIC final movies back to HDV in order to reduce the total TB's necessary to archive all our final movies.

My question is whether i should expect any significant quality loss when i transcode the files back to HDV?

Any knowledgable advice is much appreciated!

regards,
Will Johnston


Return to posts index

Shane Ross
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 14, 2011 at 4:05:33 pm

[will johnston] "My question is whether i should expect any significant quality loss when i transcode the files back to HDV? "

Well...do a test and see. But yes, compressing and then compressing...especially back to a GOP format...will result in quality loss. Do a small test and see for yourself.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


Return to posts index

will johnston
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 17, 2011 at 4:23:30 pm

Thanks, i've converted a file and am trying to work out the best method to really finely compare the two images.

I was planning to place both videos in sync on a timeline, cropped both and place them next to each other so that i would be able to examine closely and compare them on a frame by frame basis.

but i just realized that for one of the files, it will have to be sitting on a sequence which has a different setting. Will that invalidate the side by side comparison? Or does someone know the proper method for doing that?

I would like to take a closer look than just playing the videos next to each other, and hopefully can examine frame by frame.

appreciate the advice!


Return to posts index


will johnston
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 17, 2011 at 5:25:23 pm

have been fooling around further with it...

in order to try and keep it "equal" i've imported both AIC and the HDV conversion into a sequence with ProRes HQ setting (so that one wouldnt be in its native setting, and the other not), and exported that.

Now i have the two images side by side and can scroll through frame by frame to comare... and i can see absolutely no difference between the two.

that would seem to answer it, but could there be a flaw in my method of side by side comparison?


Return to posts index

David Roth Weiss
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 17, 2011 at 6:42:07 pm

[will johnston] "Now i have the two images side by side and can scroll through frame by frame to comare... and i can see absolutely no difference between the two."

You don't have a monitor good enough to see the difference or loss in in a first generation video file using AIC. However, if you go down several generations you'll quickly see a difference, as AIC discards more color information than ProRes. That's the difference between a high-performance codec and a typical highly compressed codec.

David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
http://www.drwfilms.com

Don't miss my new Creative Cow Podcast: Bringing "The Whale" to the Big Screen:
http://library.creativecow.net/weiss_roth_david/Podcast-Series-2-MikeParfit...

POST-PRODUCTION WITHOUT THE USUAL INSANITY ™


Creative COW contributing editor and a forum host of the Business & Marketing and Apple Final Cut Pro forums.


Return to posts index

will johnston
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 18, 2011 at 1:19:21 pm

So that seems to clarify for me that transcoding back to HDV (which was the original source) will be fine as far as preserving the image quality. Are there any other reasons not to use HDV, but instead move to another format like h264 mov in HD?

One other issue im a little unclear, in regards to "...AIC discards more color information than ProRes.":
Does that matter considering the fact that the original source is HDV, which captures less (i thought) color information than AIC in the first place? For me the analogy would be starting off with a low bitrate video file: no matter how much bandwidth you throw at it when you re-encode it, you arent going to gain quality.

Thanks for the advice David (or anyone else who may have some thoughts on it).

best
Will


Return to posts index


David Roth Weiss
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 18, 2011 at 9:34:43 pm

[will johnston] "Are there any other reasons not to use HDV, but instead move to another format like h264 mov in HD?"

Don't ever edit h.264 in FCP legacy, it's not recognized by FCP as a editing codec.

[will johnston] "...AIC discards more color information than ProRes.":
Does that matter considering the fact that the original source is HDV"


Of course it matters, as HDV is already a highly compressed MPG2 codec. So, transcoding to AIC throws out even more information. The objective is not to make it better with ProRes, but rather not to make it worse by transcoding to AIC.

You can edit HDV native, but HDV is a very processor intensive codec. Even editing HDV in a ProRes sequence will render faster that HDV in an HDV sequence.

David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
http://www.drwfilms.com

Don't miss my new Creative Cow Podcast: Bringing "The Whale" to the Big Screen:
http://library.creativecow.net/weiss_roth_david/Podcast-Series-2-MikeParfit...

POST-PRODUCTION WITHOUT THE USUAL INSANITY ™


Creative COW contributing editor and a forum host of the Business & Marketing and Apple Final Cut Pro forums.


Return to posts index

will johnston
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 23, 2011 at 9:09:54 am

"Don't ever edit h.264 in FCP legacy, it's not recognized by FCP as a editing codec."

good point... Is there any other known downside to archiving the material as HDV? For example, does encoding from this format produce worse results than from AIC or Pro-Res, or any other reason i should avoid saving all our masters as HDV?

We often have to re-encode for broadcast, so i hesitate to convert everything to HDV if there is any chance i'll regret it later... But on the other hand it would free up a lot of space and simplify matters (not having to swap around so many disks when accessing the content, etc.

Thanks gentlemen,

Will


Return to posts index

Shane Ross
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 23, 2011 at 4:24:43 pm

[will johnston] "Is there any other known downside to archiving the material as HDV? "

Yes. HDV sucks as a codec. Especially if the footage didn't originate from an HDV camera. It's compressed in an oddly unique way (GOP - Group of Pictures). Unless the camera shot the footage was HDV, I would not convert to HDV. Horrid idea.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


Return to posts index


will johnston
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 23, 2011 at 5:11:46 pm

Hi Shane
The footage actually did originate as HDV (shot on sony z1's) but was transcoded to AIC for editting, and our masters are therefore AIC.
In this case would you still consider it unadvisable to transcode back to HDV?

cheers,
Will


Return to posts index

Shane Ross
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 23, 2011 at 5:34:28 pm

[will johnston] "In this case would you still consider it unadvisable to transcode back to HDV?"

Yes! Bad bad bad bad! Compressed format transcoded (recompressed) to AIC, a full frame format opposed to GOP format...then transcode (recompress again) back to HDV? No no no no no no no! Ick!

But....you have the tapes. So, why archive any of the QT files? Just recapture if you need to.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


Return to posts index

will johnston
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 23, 2011 at 7:55:29 pm

no we don't have the tapes, reused or threw these out long ago.

To be honest, I actually cannot see any difference between the two (the first beingAIC material which was converted from HDV source, the second being the same footage which was then converted once more back to HDV in compressor) in a side by side, frame by frame comparison... maybe, just maybe it appears that some areas of a few frames have slightly deeper color (but honestly, i've looked at it for hours frame by frame and am not even sure of that).

but i guess i'll take everyone's word for it. I really dont want to end up regretting it later... we put way too much work into this material.

thanks for the advice everybody.


Return to posts index


Shane Ross
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Dec 23, 2011 at 9:38:28 pm

You threw away or reused the source tapes? Words fail me. Well, polite words anyway.

Those $5 tapes were the best, most reliable and highest quality way to archive your footage. And instead opted to save a highly compressed version, on a format that will fail given time (hard drives fail. Only a matter of time).

So yeah. Words fail me.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


Return to posts index

will johnston
Re: Transcoding from Apple intermediate Codec back to HDV for archival purposes?
on Jan 2, 2012 at 10:32:40 pm

You threw away or reused the source tapes? Words fail me. Well, polite words anyway.

Those $5 tapes were the best, most reliable and highest quality way to archive your footage. And instead opted to save a highly compressed version, on a format that will fail given time (hard drives fail. Only a matter of time).

So yeah. Words fail me.


really? i have to say that my experience with tapes as an archival method as been far different. We used to save our masters on tape, then after a few years we realized that many of them developed video and audio glitches, and we had to spend a few months of manpower in recapturing and correcting (as best as possible) these problem glitches.

As far as keeping the master source tapes, have you really never encountered problems with recapturing? Because we've had plenty of them... What to do when you're trying to recapture source material for a project and you have a tape causing dropped frames (which happened a lot!). its a nightmare. After experiencing this problem many times, we started keeping the captured video files on disk just in case we ever needed to go back to the project.

Archiving to tape proved itself to be a huge liability (for us anyways) and i would never consider doing that again. Now we keep our masters on 3 different sets of hard disks, and will soon add a 4th set for further security. We not only keep copies in different locations, and different cities, but make sure there's always one on another continent. If there is a better way im all ears, but i can't believe that mini dv tape is it, just from personal experience.

regards,
Will


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]