Does A/V to DV pass-thru decrease picture quality ?

[scottb721]

I captured some TV on the weekend using the A/V to DV pass-thru feature of my Sony PC108E miniDV camera. Cam to PC was Firewire.

I had aerial coming into VCR and the camera was hooked to the VCR's A/V out. TV was being viewed on the VCR's RF out.

The process was a breeze and I did 4 hrs of video without dropping a single frame.
I encoded the file to DVD, 8000k/s variable bit rate, but the final product was a bit grainy or "noisy".
There was no mpeg artifacting though.
The capture and encoding app was Media Studio Pro.

The picture coming into my VCR looked good on the TV.

Is this a result of the A/V to DV function or something else ?

I've done analog captures in the past that looked as good as the original TV picture but this is not the case here. I doubt the encoding to mpeg would have caused it.

Thanks

[danplnsk]

I find it hard to believe that you encoded 4 hours of video to one DVD in 8000 kbs. If it is to one DVD it went down to about 2000 kbs, hence the low quality.

[jday]

scottb721,
danplnsk's comments are most definitely your problem. To just explain a little more. You said you encoded at 8,000k/s variable bit rate (VBR). The VBR is the culprit here. I don't know what the final average bitrate would have been, but danplnsk is probably pretty close. If you want the quality of your dvd to be as good as possible, you need to encode it at a higher bit rate. You can do this by selecting constant bitrate (CBR), but if you select 8,000 k/s CBR you will only get approximately 1 hour of video on a single-layer dvd (commercial dvds are dual layer so can contain approximately 2 hours).

So, you have to choose between putting more video at a reduced quality on a dvd or burning more dvds in high quality with less video on each.

[redwudz]

Just to add, you could encode at 1/2 DI (352 X 480) and make a little better use of the available bitrate. 2000Kbs may be useable then.

[MpegEncoder]

scottb721,
danplnsk's comments are most definitely your problem. To just explain a little more. You said you encoded at 8,000k/s variable bit rate (VBR). The VBR is the culprit here. I don't know what the final average bitrate would have been, but danplnsk is probably pretty close. If you want the quality of your dvd to be as good as possible, you need to encode it at a higher bit rate. You can do this by selecting constant bitrate (CBR), but if you select 8,000 k/s CBR you will only get approximately 1 hour of video on a single-layer dvd (commercial dvds are dual layer so can contain approximately 2 hours).

So, you have to choose between putting more video at a reduced quality on a dvd or burning more dvds in high quality with less video on each.

VBR is not a culprit. An 8,000 kbps (AVG) VBR file is exactly the same size as a 8,000 kbps CBR file.

The bits are just distributed differently. A VBR mpeg-2 video will vary the bitrate so as to attempt to use them where they are needed.

Undoubtly, his encodes were not 8,000 kbps (AVG) VBR or he would only get one hour of video on a single layer DVD.

I agree with danplnsk

[lgh529]

VBR is not a culprit. An 8,000 kbps (AVG) VBR file is exactly the same size as a 8,000 kbps CBR file.

The bits are just distributed differently. A VBR mpeg-2 video will vary the bitrate so as to attempt to use them where they are needed.

Actually, this isn't correct either. VBR files are usually smaller than the same file encoded using CBR. The amount is completely dependent upon how good the video quality is. Home videos that are full of shakes and zooms wreak havoc on MPEG encoders and those files don't benefit from a huge file size decrease in file size.

Variable bit rate files are just that, variable. So instead of all the video being 8kb/sec it varies based upon the redundancy in the video. If your encloding a documentary where 60% of the video never changes, then VBR file sizes will be much smaller because there is enough redundancy in the video. When the video gets more action, the the bitrate increases as required.

Back to the original question - I have a Sony camcorder with pass-thru and a ADVC-100 digital video converter. I have not found any difference between the quality of the analog conversion between the two. I typically use the ADVC more because its more convenient that breaking out the camcorder, but the quality is vitually indistinguishable.

By the way, this has nothing to do with the aerial (antenna for us in the USA) connected to your VCR.

Your authoring application probably re-encoded your file to fit your whole 4 hours on to one DVD even though you picked 8kb/sec. Run a bitrate viewer on the file and see what the actual rate is.

If you still are having trouble, please provide more details, like what were you encoding, what encoder, what authoring software, etc.

Good Luck

[bugster]

VBR is not a culprit. An 8,000 kbps (AVG) VBR file is exactly the same size as a 8,000 kbps CBR file.

The bits are just distributed differently. A VBR mpeg-2 video will vary the bitrate so as to attempt to use them where they are needed.

Actually, this isn't correct either. VBR files are usually smaller than the same file encoded using CBR. The amount is completely dependent upon how good the video quality is.

Not quite right.
MpegEncoder said that an 8,000 kbps AVERAGE BITRATE VBR file is exactly the same size as an 8,000 kbps CBR file. He is 100% correct (within the limits of the encoder sticking to the user supplied settings). The difference is that a VBr encode will spread the data across multiple frames with some taking more bitrate and other less whil a CBR encode will allocate exactky the same amount of data (bitrate) to each GOP. Its the Average bitrate across the whole movie that is used to determine the file size.
Of course if you are using a quality based VBR encoding method (such as TmpGenc's CQ mode), then you are right in that the bitrate will vary with the motion in the video, but the drawback to these methods is that you cannot predict the final filesize in advance.

I agree with home video eating up bitrate tho!

[edDV]

[quote="lgh529"]

...

Back to the original question - I have a Sony camcorder with pass-thru and a ADVC-100 digital video converter. I have not found any difference between the quality of the analog conversion between the two. I typically use the ADVC more because its more convenient that breaking out the camcorder, but the quality is vitually indistinguishable.

...

This is because Canopus licensed the Sony technology for their hardware DV codec. The chip in the ADVC (and other Canopus products) has the same roots as the one in your Sony camcorder. Canopus made a big deal about using the same Sony technology back when they introduced their higher end DV capture cards.

[scottb721]

I should clarify the situation a little.
I captured 4hrs but that was spread across two 2hr captures. Each of which had the ads removed reducing each file to 1hr30min.
Each 1hr30min clip was encoded at 6000k VBR (not 8000, my apologies) at put on it's own disc.

When I play the DVD on the PC it doesn't look too bad.

Whilst on the subject, since TV isn't full D1 res perhaps 352x576 is a better choice. Even more so with VHS to DVD.

[edDV]

Did it look good before you encoded it to MPeg2?

Your DV capture file should have looked very good or there is a problem upstream.

What did you use to view the DVD on the computer monitor?

Did it look good played on the DVD player and TV?