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Unwanted compression

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Unwanted compression

Postby pierrenev » Wed Sep 28, 2011 10:33 pm

Can someone explain me why MF7 compresses the files more than necessary or requested? Here is my problem.
I burn some large files that should fit on a 4.7GB DVD disc. When I try to burn them, MF7 puts out a message that the file needs to be compressed more because of oversize.
I try to "outsmart "the system by choosing the double layer option and it accepts it and starts rendering without any message.
At the end, though, my ISO file is only about 3.8 or 3.9GB. Does that mean that I am loosing part of the quality? Or is MF7 overestimating the resulting size and giving me a false warning?
My files are MPEG2 files and I set the custom settings at the highest quality (100), variable 8264 kbps (maximum) LPCM audio, upper field.
Pierre
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Re: Unwanted compression

Postby DVDDoug » Thu Sep 29, 2011 12:00 am

is only about 3.8 or 3.9GB. Does that mean that I am loosing part of the quality? Or is MF7 overestimating the resulting size and giving me a false warning?
It could be miscalculating. But, if you're using the maximum bitrate, you're not loosing any potential quality. (I haven't done the experiments myself, but from what I've read going over 7000 kbps doesn't usually buy you any additional visual quality.)

If you've got a longer video that you need to compress and you want to exactly fill-up the disc, you can make larger DVD folders on your hard drive and then use a program called DVD Shrink. DVD Shrink is FREE, but it's sometimes hard to find because it can decrypt DVDs and that makes it illegal in most countries. :(

My files are MPEG2 files and I set the custom settings at the highest quality (100), variable 8264 kbps (maximum) LPCM audio
That should allow about an hour of video (assuming 8264 is constant or the average bitrate). FYI - LPCM audio has a bitrate of 1536kbps, so that's a total bitrate of 9800.

This is only an approximation because there is some rounding in the formula and some overhead in the file -
File Size in MB = (Bitrate in kbps x Playing Time in minutes) / 140
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Re: Unwanted compression

Postby pierrenev » Thu Sep 29, 2011 12:56 am

DVDDoug wrote:
is only about 3.8 or 3.9GB. Does that mean that I am loosing part of the quality? Or is MF7 overestimating the resulting size and giving me a false warning?
It could be miscalculating. But, if you're using the maximum bitrate, you're not loosing any potential quality. (I haven't done the experiments myself, but from what I've read going over 7000 kbps doesn't usually buy you any additional visual quality.)

If you've got a longer video that you need to compress and you want to exactly fill-up the disc, you can make larger DVD folders on your hard drive and then use a program called DVD Shrink. DVD Shrink is FREE, but it's sometimes hard to find because it can decrypt DVDs and that makes it illegal in most countries. :(

My files are MPEG2 files and I set the custom settings at the highest quality (100), variable 8264 kbps (maximum) LPCM audio
That should allow about an hour of video (assuming 8264 is constant or the average bitrate). FYI - LPCM audio has a bitrate of 1536kbps, so that's a total bitrate of 9800.

This is only an approximation because there is some rounding in the formula and some overhead in the file -
File Size in MB = (Bitrate in kbps x Playing Time in minutes) / 140


Thanks.
I just wanted to make sure that I was not losing any quality. One of my DVD's is about 65 minutes and it worried me to see that it only used 3.7GB, after the compression. I don't know if it makes any difference, but I use exactly the same settings (quality 100, 8264 kbps, etc) when I edit my clips in VS4, before I bring them in my MF7 project. Anyway, the DVD quality seems quite good when I view the on the TV.
Thanks again.
Pierre.
I also use DVDshrink and it works very well and amazingly fast. This is one of the few programs that can open ISO files (from disk or computer) and let you extract part of the file. I use it a lot when I need to extract some clips from previous DVDs that I made.
pierrenev
 
Posts: 69
Joined: Thu Aug 16, 2007 5:40 pm
Location: canada
operating_system: Windows 7 Home Premium
System_Drive: C
32bit or 64bit: 64 Bit
motherboard: AMD phenom II X6
processor: p7 - 6 core
ram: 8GB
Video Card: AMD Radeon HD 6450 512MB dedicated
sound_card: Sound Max Integrated Digital Audio
Hard_Drive_Capacity: 3300 GO
Monitor/Display Make & Model: HP 2509b LCD

Re: Unwanted compression

Postby maxblack » Fri Sep 30, 2011 6:01 pm

pierrenev wrote:I just wanted to make sure that I was not losing any quality. One of my DVD's is about 65 minutes and it worried me to see that it only used 3.7GB, after the compression.

When I do the math, it seems the video alone should have take 3.8GB, not yet adding-on the audio.

Was it obvious that MF was re-encoding when you built the disc? It would have taken a very long time again like the original render.

What is the actual bitrate of your LPCM audio?
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