FAQ - DVR-Compress

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Kimi
Programmierer
Beiträge: 3326
Registriert: 13.08.2005, 18:07

FAQ - DVR-Compress

Beitragvon Kimi » 26.11.2006, 17:04

In this you find the most important questions and answers about DVR-Compress.

<a href='#1' target='_self'>Are there any limitations in functionality during trial period?</a>
<a href='#2' target='_self'>What is the quality I can expect?</a>
<a href='#3' target='_self'>What happens if the recordings on a DVD have different data rates?</a>
<a href='#4' target='_self'>What is the lowest data rate where no further compression is possible?</a>
<a href='#5' target='_self'>What happens if a title cannot be compressed any further?</a>
<a href='#6' target='_self'>How can I detect if compression is too high?</a>
<a href='#7' target='_self'>How much time will the compression process take?</a>
<a href='#8' target='_self'>Why is this that fast? Reencoding does take hours usually!</a>
<a href='#9' target='_self'>What is the difference between compression and reencoding?</a>


<a id='1'></a>:arrow: <b>Are there any limitations in functionality during trial period?</b>
No.
All functions are available for 30 days. After this you have to purchase a licence if you want to continue using the software.

<a id='2'></a>:arrow: <b>What is the quality I can expect?</b>
That depends on the quality of the source material and the neccessary compression rate. The higher the compression rate the poorer the resulting quality will be.
Does a recording already have a low data rate (lower than 2,5MBit/s) then the result will be recognized as poor even at low compression rates.

<a id='3'></a>:arrow: <b>What happens if the recordings on a DVD have different data rates?</b>
All recordings will be compressed by the same percentage. So if a DVD is 20% too large for the inserted media all recordings will be compressed by 20%. This does not depend on the data rates of each title.

<a id='4'></a>:arrow: <b>What is the lowest data rate where no further compression is possible?</b>
That depends on the video resolution:
480x576: 1.4Mbit/s
704x576: 1.6Mbit/s
720x576: 1.7Mbit/s
Also the number of audio tracks is important, because they are NOT compressed.

<a id='5'></a>:arrow: <b>What happens if a title cannot be compressed any further?</b>
If possible - and available - the other titles are compressed with an higher factor. If this is not enough the DVD will be too small for the inserted media and there will be an error message before burning the DVD.

<a id='6'></a>:arrow: <b>How can I detect if compression is too high?</b>
In general you will notice the quality being poor before the minimal technical data rate is reached - so going to the limits doesn't make sense anyway
If the picture starts to get blocky or faces get dizzy or smooth your should consider to split your recordings on multiple DVD.

<a id='7'></a>:arrow: <b>How much time will the compression process take?</b>
As a rule of thumb about 15 minutes (AMD Athlon 3,2GHz, new S-ATA hard drive). Of course you have to consider the size of the material, the power of the CPU used and the performance of the hard drive(s).
In general applies: if source and destination directories are located on two different hard drives (does not apply for 2 partitions on the same drive) can speed up the process by up to 20%.
The amount of internal memory (RAM) does not noticably affect compression speed.

<a id='8'></a>:arrow: <b>Why is this that fast? Reencoding does take hours usually!</b>
DVR-Compress does use the MPEG video information and the structure of the GOPs, so only the content of the remaining MPEG blocks has to be compressed. This requires considerably lower CPU power.

<a id='9'></a>:arrow: <b>What is the difference between compression and reencoding?</b>
During reencoding each single picture as to be mapped as full picture. Afterwards the MPEG-encoder has to calculate the differences and motion vectors between the pictures and only then can create GOP structures and compress MPEG-blocks. Of these steps finding the motion vectors takes most of the time and CPU power.
Compressing can use the existing GOP structures and motion vectors and only has to compress the MPEG-blocks.

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