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Akram Husseini
compressing MPEG2 file
on Jun 24, 2009 at 4:05:39 pm

Hello,

I have a number of PAL MPEG2 files, 25FPS resolution 704x576, data rate 15MB/sec. I want to try and compress them to save some space and here are the detials of what I have and want to do:

Computer: PC
Operating System: Windows 7 RTM build 7260
Software used: Sorenson Squeeze 5.1.0.12
Source codec: MPEG2, PAL, 25FPS, Resolution 704x576, Data Rate: 15MB/sec, screen type 4:3
Destination codec: Not sure which to use, but thinking of either DVD format or WMV, whatever is closest to the origional quality
Type of destination use: Just want to store on disc for the time being, possibly to DVD in the future.

in squeeze, I looked at the available formats, like DVD_PAL_16x9_Lg, DVD_PAL_16x9_Sm, DVD_PAL_Lg, DVD_PAL_Sm but I can't tell what is the difference between them. What does the "Lg" or "Sm" mean? and if my origional video is 4:3, is using 16:9 ok? or should I look for another option? also I tried using DVD_PAL_Lg and DVD_PAL_Sm but they seem to produce 2 files, one of them has video which has a .m2v extension, and when I play it there is no sound. another file is also produced with an extension .m2a which I think might have the audio but I'm not really sure. why doesn't it produce the file in the extension .mpg and has both video and audio toghether? I'm I doing something wrong? please help, Thank you


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Dave Puryear
Re: compressing MPEG2 file
on Jun 25, 2009 at 1:27:27 pm

If your source is 4:3, then we recommend keeping your output 4:3. Therefore, use DVD_PAL_Lg.

Regarding file types, you need to open the encoding preset of choice and select Program Stream output instead of Elementary Streams.

http://forum.sorensonmedia.com/f/sfaq.php#f18



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Akram Husseini
Re: compressing MPEG2 file
on Jun 25, 2009 at 4:52:43 pm

David,

Thanks for your reply. I managed yesterday to find the option to make 1 video/audio ,mpg file, I think I used DVD_PAL_Lg or DVD_PAL_Sm not sure, I squeezed the 2.1GB but the result was a 5GB file! can you beleave that? even though the average bitrate in the squeeze settings was around 8-9 MB/sec. I'm really getting second thoughts now about squeeze, also I'm thinking it's useless to try to compress an already compressed MPEG file. is 2.1GB file ok for a 1:30 hours video, with the above resolution and 15MB/sec bitrate? do you think there is a better solution than squeeze for compressing files on disk? I just want to keep a decent quality of my recordings, and have the possibility of moving them into DVD if I want at some point, while not using too much space on disk.

Also squeezing the file took a very long time, hours. is that normal for a file with this size? I have 2GB of ram, and an Intel Core 2 Duo 2.8Mhz E7400 CPU, and plenty of disk space, running 32-bit windows 7 build 7260.


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Dave Puryear
Re: compressing MPEG2 file
on Jun 25, 2009 at 6:47:11 pm

[Akram Husseini] "I think I used DVD_PAL_Lg or DVD_PAL_Sm not sure"

Take notes, please.

[Akram Husseini] "I squeezed the 2.1GB but the result was a 5GB file! can you beleave that? even though the average bitrate in the squeeze settings was around 8-9 MB/sec"

Yes, I can believe that. The longer you do this, you'll see more examples.

[Akram Husseini] "I'm really getting second thoughts now about squeeze,"

There's nothing wrong with Squeeze.

[Akram Husseini] "also I'm thinking it's useless to try to compress an already compressed MPEG file"

That depends on your goals.

[Akram Husseini] "is 2.1GB file ok for a 1:30 hours video, with the above resolution and 15MB/sec bitrate?"

It seems low. We need to know more about the source file. Is it CBR or VBR? MediaInfo.exe is a great tool for analyzing media files.

[Akram Husseini] "do you think there is a better solution than squeeze for compressing files on disk"

That's a loaded question. Again, there's nothing wrong with Squeeze. It supports many of the latest and greatest codecs.

[Akram Husseini] "Also squeezing the file took a very long time, hours. is that normal for a file with this size?"

Yes. I'd get used to it. Run jobs overnight if you have to.


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Akram Husseini
Re: compressing MPEG2 file
on Jun 25, 2009 at 11:00:15 pm

Thanks again for you reply david, you asked if it's CBR or VBR, I'm not sure, I recorded the file using a software called mfaraj dreambox viewer V3.0, this application uses a software module called wingrab to record from the dreambox 500 receiver. there is no options on the output, it always creates an MPEG2 file with a .mpg extension.

so I can use MediaInfo.exe to get more info on this video file? where do I get MediaInfo.exe? is it free?

thanks a lot for taking the time to answer my noob questions :)


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Dave Puryear
Re: compressing MPEG2 file
on Jun 26, 2009 at 2:13:20 pm

mediainfo.sourceforge.net


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Akram Husseini
Re: compressing MPEG2 file
on Jun 26, 2009 at 3:03:04 pm

Thanks Dave,

I tried MediaInfo and here is what it says about the file:

General
Complete name : Prime 17.mpg
Format : MPEG-PS
File size : 2.15 GiB
Duration : 1h 30mn
Overall bit rate : 3 409 Kbps

Video
ID : 224 (0xE0)
Format : MPEG Video
Format version : Version 2
Format profile : Main@Main
Format settings, Matrix : Default
Duration : 1h 30mn
Bit rate mode : Variable
Bit rate : 3 210 Kbps
Nominal bit rate : 15.0 Mbps
Width : 704 pixels
Height : 576 pixels
Display aspect ratio : 4/3
Frame rate : 25.000 fps
Colorimetry : 4:2:0
Bits/(Pixel*Frame) : 0.317
Stream size : 2.03 GiB (94%)

Audio
ID : 192 (0xC0)
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 2
Duration : 1h 30mn
Bit rate mode : Constant
Bit rate : 64.0 Kbps
Channel(s) : 1 channel
Sampling rate : 48.0 KHz
Resolution : 16 bits
Video delay : -72ms
Stream size : 41.4 MiB (2%)


So can you tell if it's CBR or VBR? btw what does CBR and VBR stand for?

For the above file, do you think it's possible to compress it without lousing a significant amount of quality? or is it better to just leave it as it is?

thanks!


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Dave Puryear
Re: compressing MPEG2 file
on Jun 26, 2009 at 3:58:48 pm

CBR = Constant Bit Rate mode
VBR = Variable Bit Rate mode

Your file is VBR, and I'd keep it the way it is.

You would probably benefit from doing some introductory reading on media compression theory. There are several books, websites, wikis, etc. available on the subject. For starters, try http://en.wikipedia.org/wiki/Video_compression. There are enough hyperlinks in there to keep you busy for a while.


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Akram Husseini
Re: compressing MPEG2 file
on Jun 26, 2009 at 5:02:57 pm

Dave, Ok I guess I will keep it as it is then for now. thanks for taking the time to explain everything and help me :) have a nice day!


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