How to change data rate?

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anny
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How to change data rate?

Post by anny »

Hello! I would like to make video smaller as possible without quality loss, so - to save it as MOV file with smaller bit rate (or maby data rate). I would like, how to reduce it for smaller mov file size.
Gorf
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Re: How to change data rate?

Post by Gorf »

You can only ever decrease the data rate with no loss of quality if you use what is known as a lossless codec (Such as HuffYUV).

Your question should really be "how do I minimise quality loss"? That yields so many variables it's impossible to answer. It depends on the dimensions of the video, what's happening in it, and what compression it's already been subjected to.

Your best bet is to decide out what file size you want it to be in MB, divide that by the duration in seconds then multiply that by 8388 to get the data rate in kbps
So for a 2½ minute vid that we want to fit into 10 MB the maths is:
10 ÷ 150 x 8388 = 559.2 kbps

Decide the smallest pixel dimension you think you can get away with (e.g. 355x288) and recode it using that size and the calculated bitrate using a variety of codecs. Choose the best looking one from the various outputs. It may change from one piece of footage to another even iff all the other variables (size, duration, bitrate) stay the same.
Gorf
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Re: How to change data rate?

Post by Gorf »

Don't forget your audio. Using 11 KHz mono uses an eighth of the space needed for CD quality audio.
anny
Posts: 7
Joined: Sat Oct 02, 2010 6:26 pm
operating_system: Windows XP Pro
System_Drive: C
32bit or 64bit: 32 Bit
motherboard: I have PORTATIVE COMPUTER
processor: 1.30 gigahertz Intel Celeron M -PortativeComputer
ram: 32GB
Video Card: SoundMAX Integrated Digital Audio
sound_card: SoundMAX Integrated Digital Audio
Hard_Drive_Capacity: 40.00 Giga
Location: Texas

Re: How to change data rate?

Post by anny »

It is video, what was made in Premiere Pro as DV AVI PAL compression format. It is 447 MB big, but I would like it to be max about 100 MB big.
Gorf
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Re: How to change data rate?

Post by Gorf »

Your best bet is to recode it using MPEG-2 with a bitrate of 5400 kbps VBR. Use mpeg audio at 256 kbps unless you can be sure the PCs it will be playing back on have an AC3 decoder, in which case use AC3 at 224 kbps

The resulting MPG file will be just under 100 MB
anny
Posts: 7
Joined: Sat Oct 02, 2010 6:26 pm
operating_system: Windows XP Pro
System_Drive: C
32bit or 64bit: 32 Bit
motherboard: I have PORTATIVE COMPUTER
processor: 1.30 gigahertz Intel Celeron M -PortativeComputer
ram: 32GB
Video Card: SoundMAX Integrated Digital Audio
sound_card: SoundMAX Integrated Digital Audio
Hard_Drive_Capacity: 40.00 Giga
Location: Texas

Re: How to change data rate?

Post by anny »

Is there anyway, how to make frame size to be user defined (752x576)? Because video have aspect ratio 4:3, but place, where it will be shown do not understand aspect ratios, so could to frame horizontal size 720 add 32 and it could be looking good with no aspect ratio.
Gorf
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Re: How to change data rate?

Post by Gorf »

Yep all the settings are in the output dialog. You need to use "user defined" frame size
anny
Posts: 7
Joined: Sat Oct 02, 2010 6:26 pm
operating_system: Windows XP Pro
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32bit or 64bit: 32 Bit
motherboard: I have PORTATIVE COMPUTER
processor: 1.30 gigahertz Intel Celeron M -PortativeComputer
ram: 32GB
Video Card: SoundMAX Integrated Digital Audio
sound_card: SoundMAX Integrated Digital Audio
Hard_Drive_Capacity: 40.00 Giga
Location: Texas

Re: How to change data rate?

Post by anny »

How to do it, if row USER DEFINED is unactive, when the output fomat is MPEG?
Gorf
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Re: How to change data rate?

Post by Gorf »

Is it set to DVD in the compression tab? That would have the effect you're describing.

It's also worth pointing out that mathematically, you need to be resizing to 768x576 for the correct aspect ratio, not 752x576
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