Proxi codec

[erdna]

Does the Proxi settings in VS11.5+ have any effect on the rendered hdv/avchd content? Quality loss?

[Ken Berry]

Welcome to the forums!

If you start a project consisting of AVCHD files, but use SmartProxy, edit the proxy files, then the changes are applied to the AVCHD files in the background but not changing the original properties. If you then insert the edited AVCHD into the burning module, and ensure that 'Do not convert compliant MPEG files' is ticked, VS will simply burn the AVCHD to disc using its existing properties and quality.

That being said, mpeg -- which is what AVCHD is, after all -- is inherently a lossy format, meaning there will be small but cumulative losses of data (in other words, quality) each time it is rendered. But given that the original is very high quality high definition video, one or two renders is not going to cause a loss of quality which is detectable by the naked eye.

The other thing you need to be prepared for is that the process of editing AVCHD and rendering is VERY slow. AVCHD is very demanding of computer resources. To give an example, yesterday I was rendering high quality high definition HDV format mpeg-2 (which uses a frame rate of 30,000 kbps) to AVCHD (with a framerate CBR of 16,800 kbps). I was using my Core 2 Duo 2.4 GHZ laptop running Vista Home Premium. It does not need to use SmartProxy. The project itself was 31 minutes long, and it took 4 hours 10 minutes just for the rendering to occur. So be patient. Go shopping, have a meal, read a book, watch TV, while AVCHD is being rendered...

[erdna]

Thanks Ken. And yes, I know rendering AVCHD is slow, also on my core duo PC.
I got a few additional questions:
-Does setting the Proxi to 720x560 or 360x280 make no difference in the rendered video quality level?
-Does the rendering effectively process all data or just the edited (text, crosovers..) parts? Does that ticking "Do not convert compliant MPEG files" avoid that total rendering?
-If you render with CBR/16800kbps, is such a rendered AVCHD project still OK for burning an AVCHD DVD? Is DVD not limited to data rates of ~9000kbps?

[Ken Berry]

1. I don't know if 360 x 280 makes any difference. I have never used it. So I am afraid, unless someone else here knows the answer from experience, that you just might have to experiment yourself to see.

2. As far as I am aware, when the proxy edits are applied to the original video, only the video around the edits is affected. In other words, it is like SmartRender. However, I stress here that my experience using SmartProxy is limited to my very early days of using the AVCHD format. I very quickly learned I needed to use a computer with at least a Core 2 Duo processor, and in fact bought a Core 2 Quad, which is fast enough to not need to use SmartProxy.

As for the 'Do not convert' box, that always depends on what you want to produce. But if you want, say, to produce an AVCHD DVD, and use video which is already AVCHD, then ticking that box means that it will NOT be rendered again during the burning process, regardless of the properties set out in the little window above the Do not convert button.

3. Your third question about CBR/16800 kbps indicates that you might not fully understand the state of current technology. A *standard* definition DVD cannot have a combined video and audio bitrate which is higher than 10,000 kbps. However, high definition consumer video cameras use much higher bitrates - up to 35,000 for some formats. AVCHD uses bitrates of anything between (typically) 12,000 -- 17,000. It can also be either VBR or CBR.

Now, another aspect of current technology is that if you cannot afford a Blu-Ray burner and the cost of Blu-Ray discs at the moment, there is a midway possibility which allows you to burn a hybrid disc, using high definition AVCHD but burned in that format to a standard DVD.

The downside of this hybrid disc is that it can ONLY be played in a Blu-Ray player rated to 'see' the AVCHD. Not all of them will do this, apparently, but one that definitely does, and which a lot of people have these days, is the Sony PlayStation 3. I just bought one a couple of days ago, and believe me, it works beautifully to play AVCHD hybrid discs. You just insert the disc, PlayStation automatically detects the format on the disc, and up comes the disc menu, just like on a standard DVD. But of course, if your PlayStation is connected, as mine is, via HDMI cable to a high definition TV, you can see your hybrid DVD play back in true high definition format! Believe me, its wonderful...

The other slight downside is that, because AVCHD uses a much higher bitrate than standard definition, you can only burn about between 30 - 40 minutes of AVCHD to a single layer DVD. But this doesn't worry me as I currently buy my DVD blank discs for around 26 cents each.

To give you an idea, the first hybrid disc I made the other day used the VS default AVCHD settings, which includes VBR max. 15000 kbps, which in effect means a relatively low average bitrate of around 12000 kbps. Using this, I managed to fit 56 minutes of AVCHD on a single layer DVD. It played back well on the PlayStation and was clearly high definition -- but definitely not of the same quality as the original from my high def Canon HV20 camera played back via HDMI on the same high def TV. So I am now experimenting with using a higher bitrate and CBR of 16,800 kbps to see if the playback quality improves. I have a disc currently burning and will report back on its quality. I can fit nearly 40 minutes on the DVD using that bitrate, by the way.

A footnote to the last para is that I have found that VS11.5+ is somewhat limited still in the properties you can use for AVCHD in the editing module. The default seems to be VBR 15000 kbps. There is also no way of using Movie Template Manager to make an AVCHD template with a higher, constant bitrate. So I have in fact been putting my original HDV/mpeg-2 videos into the burning module, after selecting 4.7 GB AVCHD as the output. That way, it doesn't matter whether 'Do not convert' is ticked or not as the HDV video is not compliant with the AVCHD standard, and will thus be rendered using the properties in the little window above. And you *can* change those properties to use a higher AVCHD bitrate and also make it CBR rather than VBR.

But if you produce a standard definition DVD, then your high def AVCHD will of necessity be down-converted to standard definition mpeg-2 format which is compatible with the international SD DVD standard. And the quality, while still excellent compared to other SD DVDs, is still standard definition, and no longer high definition.

[erdna]

Thanks again Ken for your quick and usefull reply. I am out for one week now, and will be back then.