.avi to .mpeg2 size calculation question

erock1 · Post by **erock1** » Mon Jun 06, 2005 1:40 pm

I know using a bit rate calc. you can figure the bit rate needed to fit content to a DVD disc. Is there a way to figure what an mpeg2 file size will be after rendering it from an .avi file(s)?

My OS is ME with the Fat32 4gb limit. I want to try to figure out what total size .avi files I can capture and place in VS8's timeline in order to render an mpeg2 file no larger than my 4gb limit.

TIA,
Erock

GeorgeW · Post by **GeorgeW** » Mon Jun 06, 2005 1:46 pm

just use the combined length of your .avi files in the bitrate calculator. I'm not sure I understand what you are asking...

if you have a 45-minute .avi, and a 15-minute .avi, you use 60-minutes in the bitrate calculator (assuming one audio track and and one video angle).

Is that what you are asking?

erock1 · Post by **erock1** » Mon Jun 06, 2005 2:42 pm

GeorgeW wrote:just use the combined length of your .avi files in the bitrate calculator. I'm not sure I understand what you are asking...

if you have a 45-minute .avi, and a 15-minute .avi, you use 60-minutes in the bitrate calculator (assuming one audio track and and one video angle).

Is that what you are asking?

Thanks GeorgeW. I guess my question wasn't clear.

I'm not interested in finding out how much content can be burned on to a DVD. I'm trying to figure out how large (file size) an .avi will be after rendering to an mpeg2 file.

Example: I have a 20gb .avi file. I want to know after rendering to an mpeg2 how many gbs the resulting mpeg2 file will be before I render it. I hope that's clear.

GeorgeW · Post by **GeorgeW** » Mon Jun 06, 2005 3:21 pm

a 20gb .avi file is a "moving" target, because .avi's can be a number of different codecs (dv .avi, divx .avi, xvid .avi, uncompressed .avi, etc...).

Not knowing what type of .avi you are talking about, there is no way to give you a 100% answer because the bitrates of the .avi can differ depending on the codec used.

You go by the MINUTES of the source video, and mutliply it by your bitrate (video + audio) to give you the resulting mpeg2 file size.

In the bitrate calculator at videohelp.com/calc.htm, you can hit the Advanced button. You can then work with custom sizes by entering a bitrate -- it will tell you the resulting size. or entering a custom size, and it will give you a bitrate. But the KEY piece of the puzzle is the duration of the video to be encoded (not the size of the video to be encoded).

erock1 · Post by **erock1** » Mon Jun 06, 2005 4:14 pm

GeorgeW wrote: You go by the MINUTES of the source video, and mutliply it by your bitrate (video + audio) to give you the resulting mpeg2 file size.

In the bitrate calculator at videohelp.com/calc.htm, you can hit the Advanced button. You can then work with custom sizes by entering a bitrate -- it will tell you the resulting size. or entering a custom size, and it will give you a bitrate. But the KEY piece of the puzzle is the duration of the video to be encoded (not the size of the video to be encoded).

BINGO! Thanks GeorgeW, that's exactly what I was looking for. I have all the variables (codec, etc.). I will try it tonight.

erock1 · Post by **erock1** » Tue Jun 07, 2005 3:03 pm

erock1 wrote:
GeorgeW wrote: You go by the MINUTES of the source video, and mutliply it by your bitrate (video + audio) to give you the resulting mpeg2 file size.

In the bitrate calculator at videohelp.com/calc.htm, you can hit the Advanced button. You can then work with custom sizes by entering a bitrate -- it will tell you the resulting size. or entering a custom size, and it will give you a bitrate. But the KEY piece of the puzzle is the duration of the video to be encoded (not the size of the video to be encoded).
BINGO! Thanks GeorgeW, that's exactly what I was looking for. I have all the variables (codec, etc.). I will try it tonight.

GeorgeW (or anyone else), I'm still a bit (pun intended) confused regarding the bit rate calc. Below are the properties of my .avi file. What is confusing me is the audio bit rate.
My total .avi length is 1 hr. 20 min. The codec I use is DV Video Encoder Type 2. I'm using the calc's default Bps @ 1kbit=1000 bits. The calculator next asks for the audio bitrate. The audio properties from my .avi is compression=PCM, attributes= 32,000 hz, 16 bit stero. I didn't note the sampling rate indicated (is this important?).

Question, how do I figure what my audio bitrate is? I'm using the calc's advanced mode. The dafault audio bitrate setting on the calc seems to be 224. Entering my .avi length and leaving the audio bitrate at 224 kbits provides the following mpeg size info:
Video size=4231MB MPEG/Author Overhead= 92MB Audio Size=131MB ISO=23MB Total=4479MB This is over the 4gb limit my OS will allow.

Regardless of what audio bitrate I enter (64, 112, etc.) the calc indicates the audio size increases but the total MPEG size remains at 4479MB?

GeorgeW · Post by **GeorgeW** » Tue Jun 07, 2005 3:27 pm

for uncompressed audio (LPCM) use 1536kbps as the bitrate.

This takes up alot of space compared to Dolby Digital or mpeg audio.

NOTE: mpeg audio is ok for PAL, but it is not an NTSC Standard. So some NTSC DVD Players will not playback mpeg audio...

erock1 · Post by **erock1** » Tue Jun 07, 2005 5:05 pm

GeorgeW wrote:for uncompressed audio (LPCM) use 1536kbps as the bitrate.

This takes up alot of space compared to Dolby Digital or mpeg audio.

NOTE: mpeg audio is ok for PAL, but it is not an NTSC Standard. So some NTSC DVD Players will not playback mpeg audio...

Thanks GeorgeW. Since I'm in the US, MPEG audio is out. Let me see if I have a handle on this.

My problem is that I can not create a file over 4gb due to my Fat32 OS, ME. Since I want to be able to create the largest .mpeg2 file my OS will allow in VS8 without wasting the time on rendering only to get an error message bacause of the 4gb limit, I will use the bitrate calc to figure out how large a file my .avi will be after rendering. Since the bitrate calc provides the overhead for mpeg authoring and ISO creation, can't I just use the calc's "video size" and add the size of the audio for an approx of my total mpeg file size? When I get to the burn stage I can always adjust the bitrate down to fit the menus, etc. Does this sound right?

BTW, I have the AC3 plugin for VS8 but for the life of me I can not find a way to convert the LPCM audio of my .avi to AC3 at the Create a video file stage. The plugin only seems to allow me to convert the audio in the disc burning stage.