First off, I realize the title of this post sounds a bit arrogant. It is not my intention to be so, I am trying to be helpful and hopefully save a lot of folks time and effort and disk space. I have deep experience as a former QuickTime developer for Apple and come at this from both sides: a film maker and a programmer. I got a little frustrated reading posts where well-meaning folks are essentially suggesting the most bizarre and wasteful workflows or flat out give wrong information. In the end their workflow may work, but it is likely because of luck and their willingness to waste time with bigger data.
So there are countless threads wherein people are asking about what codec to transcode their AVCHD footage (And even other formats) to. Even if they should at all. It is a deep topic and I will limit my points to those whose footage originates in AVCHD; though much of the facts and concepts are poratble to other formats as well.
Truth is, anything more than Pro-Res Proxy for any AVCHD footage is a waste of time and space. For most projects you can transcode, edit, and finish your entire film with just Pro-Res Proxy. There is little reason to use LT, HQ, or 4444.
The short answer why is two fold: AVCHD tops out at 25mbs so any codec that is greater is useless and that your destination output is unlikely to be one that can handle the higher color space - possibly bitrate too.
Because the AVCHD spec limits maximum bitrate to 25mbs for any size video, no amount of extra bandwidth in the transcoded format will get you better video. To think otherwise is analogous to thinking if you could make $10 bill physically bigger it would buy you more stuff. You simply can't get more data from something that isn't there.
However, I can think of a few reasons that most might want to use the other ProRes codecs besides ProRes proxy (not an exhaustive list but the top 3 reasons):
1) You shoot some other HD format besides AVCHD that exceeds the 45mbs data of the proxy codec like RED, Viper, Phantom, uncompressed HD etc.
2) You have a portion of your sequence that uses green screen, lots of filters, heavy alpha channels, etc. and you don't want to wait around for the render every time you touch something in your timeline. In this case you would transcode the SFX-heavy portions from AVCHD to LT, HQ, or 4444 depending on how many effects and alpha channels and round trips you expect. Do all your wizardy in a separate sequence set to the better codec, then export using QT conversion as Proxy and drop the clip into your Proxy version timeline with the rest of the footage. You can always tweak the hi-res sequence and re-render if you need to change things.
3) Your final destination output is for a 10-bit digital cinema projector, film, or another format that is uncompressed HD; some film festivals will ask for this if you get accepted but your submission is invariably on DVD with a top bitrate of about 10Mbs.
But what about the better color grading idea that everyone is talking about with the ProRes 422 or 4444 versions? Shouldn't I use that to get the best quality grade? Maybe. It is partially true in that the app you will get finer-grained adjustments because of the wider colorspace, but your ability to adjust that finely is directly limited to your ability to see it. Is your grading monitor a $3600 sony LMD-2450MD or equivalent that has true 10-bit signal processing? If so then go for it. Or perhaps you outsource the grading to a pro colorist and she has top of line gear. Then 422 or 4444 is your best bet...maybe, read on.
However, if you are like the vast majority of us and are using stock montiors in the $1000 or less price range, then you will hardly be able to see this difference. The biggest factor though is your final output format. If it is anything on the web or a disc of some sort then all your color grading efforts - if you were even able to see the difference on your crappy monitor - will, in an instant of export, be lost in the downsampling and quantization to the lesser-grade format. And worse, you have no choice in the matter.
That last part is critical. Think about the difference between 1024 values per color channel (10-bit) color and 256 color values per color channel (8-bit). When down converting it means that possibly 3 out of every 4 colors gets pinned/quantized to some value that it wasn't originally. The point is you may not like the effect. If you keep it in 8-bit because you are going to 8-bit in the end, then well, you will always know what you are getting. I realize this is an over simplification and that ther are various sampling means within the world of video, but the principal is true: data is being thrown out.
So in summary, set your FCP Log and Transfer preference to ProRes proxy and ingest and edit away. You save gobs of HD space and won't lose a bit of quality (scenarios describe above excepted).
So there are countless threads wherein people are asking about what codec to transcode their AVCHD footage (And even other formats) to. Even if they should at all. It is a deep topic and I will limit my points to those whose footage originates in AVCHD; though much of the facts and concepts are poratble to other formats as well.
Truth is, anything more than Pro-Res Proxy for any AVCHD footage is a waste of time and space. For most projects you can transcode, edit, and finish your entire film with just Pro-Res Proxy. There is little reason to use LT, HQ, or 4444.
The short answer why is two fold: AVCHD tops out at 25mbs so any codec that is greater is useless and that your destination output is unlikely to be one that can handle the higher color space - possibly bitrate too.
Because the AVCHD spec limits maximum bitrate to 25mbs for any size video, no amount of extra bandwidth in the transcoded format will get you better video. To think otherwise is analogous to thinking if you could make $10 bill physically bigger it would buy you more stuff. You simply can't get more data from something that isn't there.
However, I can think of a few reasons that most might want to use the other ProRes codecs besides ProRes proxy (not an exhaustive list but the top 3 reasons):
1) You shoot some other HD format besides AVCHD that exceeds the 45mbs data of the proxy codec like RED, Viper, Phantom, uncompressed HD etc.
2) You have a portion of your sequence that uses green screen, lots of filters, heavy alpha channels, etc. and you don't want to wait around for the render every time you touch something in your timeline. In this case you would transcode the SFX-heavy portions from AVCHD to LT, HQ, or 4444 depending on how many effects and alpha channels and round trips you expect. Do all your wizardy in a separate sequence set to the better codec, then export using QT conversion as Proxy and drop the clip into your Proxy version timeline with the rest of the footage. You can always tweak the hi-res sequence and re-render if you need to change things.
3) Your final destination output is for a 10-bit digital cinema projector, film, or another format that is uncompressed HD; some film festivals will ask for this if you get accepted but your submission is invariably on DVD with a top bitrate of about 10Mbs.
But what about the better color grading idea that everyone is talking about with the ProRes 422 or 4444 versions? Shouldn't I use that to get the best quality grade? Maybe. It is partially true in that the app you will get finer-grained adjustments because of the wider colorspace, but your ability to adjust that finely is directly limited to your ability to see it. Is your grading monitor a $3600 sony LMD-2450MD or equivalent that has true 10-bit signal processing? If so then go for it. Or perhaps you outsource the grading to a pro colorist and she has top of line gear. Then 422 or 4444 is your best bet...maybe, read on.
However, if you are like the vast majority of us and are using stock montiors in the $1000 or less price range, then you will hardly be able to see this difference. The biggest factor though is your final output format. If it is anything on the web or a disc of some sort then all your color grading efforts - if you were even able to see the difference on your crappy monitor - will, in an instant of export, be lost in the downsampling and quantization to the lesser-grade format. And worse, you have no choice in the matter.
That last part is critical. Think about the difference between 1024 values per color channel (10-bit) color and 256 color values per color channel (8-bit). When down converting it means that possibly 3 out of every 4 colors gets pinned/quantized to some value that it wasn't originally. The point is you may not like the effect. If you keep it in 8-bit because you are going to 8-bit in the end, then well, you will always know what you are getting. I realize this is an over simplification and that ther are various sampling means within the world of video, but the principal is true: data is being thrown out.
So in summary, set your FCP Log and Transfer preference to ProRes proxy and ingest and edit away. You save gobs of HD space and won't lose a bit of quality (scenarios describe above excepted).
