Understanding extracted video quality

[smaye]

I have successfully burned about 10 DVDs now. Everything is working great thanks to this forum's help. I am trying to get a handle on what I am seeing and have a few questions.

I am recording off a HD Directivo. The SD video size is all 480 x 480 and bitrates seem to be around 2000 (m?)bps (after VRD processing ) yet the video quality can very dramatically.

What other variables do I need to consider when it comes to PQ?

Satellite broadcaster compression?
Original video quality?


Regarding encoding- If the video I have has a bitrate of about 2000 mbps and I decide to re-encode using a constant bitrate is there any value in encoding at a bitrate higher than 2000? Or, does it just create a large file?

[bits]

Smaye wrote:

What other variables do I need to consider when it comes to PQ?
Satellite broadcaster compression?
Original video quality?

Regarding encoding- If the video I have has a bitrate of about 2000 mbps and I decide to re-encode using a constant bitrate is there any value in encoding at a bitrate higher than 2000? Or, does it just create a large file?
PQ is affected by:
Original video quality, the settings used to record with the Directvo, any re-encoding done by the authoring software. As you probably already know one that thing will not affect PQ is VRD...it does not re-encode except for a frame on either side of a cut.

Re-encoding your recorded material is not a good idea because it usually leads to lower PQ. Increasing bitrate will make larger files and will reduce PQ.

For the best PQ in your setup...record at the best settings you can. If a file is too big for a single DVD then use two DVDs or use DL DVD.

[bits]

I forgot to mention this but if I understand your settings...you are recording at settings that will produce low to mediocure PQ...they will certainly not preserve the original PQ! My suggestion would be 720x480 with a VBR of 7mb to 9mb. This will result in a file size of just over 2GB per hour for most recordings.

[smaye]

I forgot to mention this but if I understand your settings...you are recording at settings that will produce low to mediocure PQ...they will certainly not preserve the original PQ! My suggestion would be 720x480 with a VBR of 7mb to 9mb. This will result in a file size of just over 2GB per hour for most recordings.


Hi bits,

On this unit (HR10-250 HD Directivo) there is no setting for PQ. It is supposedly set for the best it can be. Whenever I am done saving a VRD file a screen comes up with a lot of information. It includes bitrate. It is almost always around 2000Mbps. The only exception to this is when I get a hi-def recording which the file is about 7-8GB/hour. Of course the picture is wonderful!

[bits]

Hi bits,

On this unit (HR10-250 HD Directivo) there is no setting for PQ. It is supposedly set for the best it can be. Whenever I am done saving a VRD file a screen comes up with a lot of information. It includes bitrate. It is almost always around 2000Mbps. The only exception to this is when I get a hi-def recording which the file is about 7-8GB/hour. Of course the picture is wonderful!
Sorry but I am not familiar with your unit. How big are the non-HD files?

To clarify, you said that the PQ can vary dramatically...is that from non-HD recording to non-HD recording? From now on lets call non-HD SD(Standard Definition)

Are the HD recordings ts or tp? Are the SD recordings mpeg2?

How many SD files per DVD are you doing?

What is your authoring software?

Are you in the USA?

[smaye]

Hit bits,

Does this help?

Sorry but I am not familiar with your unit. How big are the non-HD files? If I am reading Tytool correctly SD runs about 1 GB/hour and HD runs about 8 GB/hour.

To clarify, you said that the PQ can vary dramatically...is that from non-HD recording to non-HD recording? From now on lets call non-HD SD(Standard Definition). I am speaking of differences in clarity between different SD shows. Dramatically is relative, but I am amazed that some newer SD shows look very clear as compared to some shows produced in either the '70's, 80's or early 90's.

Are the HD recordings ts or tp? Are the SD recordings mpeg2? The files come over from the HD Tivo as .ty format unless I have them muxed to mpeg2 during the extraction (which I always do).

How many SD files per DVD are you doing? Right now 2, but I can see that I could fit as many a 4. Just starting to play with doing that.

What is your authoring software? DVD-Lab Pro.

Are you in the USA? YES.

[bits]

1GB per hour for SD is probably on the side of lower PQ...not terrible but not good either.

I have found the same thing as you in terms of there being a noticable difference in PQ between SD shows and yes older shows tend to have lower PQ.

I have found, since I started recording HD transport streams, that SD shows with poor PQ are broadcast at fairly low bitrates, like around 3mb/s. Which by the way turns out to be around 1.2GB per hour....this may explain why your recording device is set to best quality but the resulting PQ is poor and the file size is smaller than expected...just a thought.

Along that same line of thought, I record SD shows with a PVR-250 capture card and it is set to record at a VBR of 7-9MB/s for all analog and digital recordings. The assumption is that the broadcast bitrate is at least that high or higher....well guess what it is not!...so I now try to record as many SD shows as ts or part of a ts. I have been recording a show called Monarch of the Glen with my PVR...found it in a transport stream one day and the PQ was better than when recorded by my PVR250 but it was almost half the size. My PVR250 was encoding it at a much higher bitrate than it was broadcast and was actually reducing the PQ...at least that is my current theory.

[smaye]

I have found the same thing as you in terms of there being a noticable difference in PQ between SD shows and yes older shows tend to have lower PQ.

I think in my case a lot has to do with Directv and their broadcasting. I don't know if it is their bitrates or compression. I have heard differing viewson how they manipulate these. However, it is pretty bad when my OTA antenna has better SD PQ as compared to satellite.

I routinely record 1966 episodes of Star Trek on my WUXP HD channel. The broadcasts are in SD, but the PQ is still phenominal. I see details I could never see before! :D

[BaysideBas]

I routinely record 1966 episodes of Star Trek on my WUXP HD channel. The broadcasts are in SD, but the PQ is still phenominal. I see details I could never see before! :DThat's because Star Trek TOS has been digitally remastered/enhanced.

[smaye]

That would explain a lot. Man! I wish I could clean up video like that.