mpeg1 to dvd bitrate?

[ludacris]

I have 3 questions:

1. I want to burn mpeg1 files that are encoded at 1150 Kb/s to a dvd. Is there any advantage to increasing the dvd bitrate above 1150? For example, I can increase the bitrate to over 3000 to fit it on one disk, but is there any advantage or should i just keep it at 1150?

2. On the same topic. If I convert those same mpeg1 files to mpeg2, is there any advantage to increasing the bitrate above 1150?

I'm sure these are newbie questions. My guess is there's no advantage to increasing the bitrate above the original file because all the data has already been lost during compression and there is no way to get it back.

3. If I convert an avi file to dvd, I'm assuming the bitrate does affect the quality because an avi file has no compression. Is this correct?

I've searched all over the internet for answers but couldn't find anything so that's why i came here.

[mats.hogberg]

1 No. VCD video can be authored straight to DVD.
2 No. Don't convert mpeg1 (if it's DVD compatible) at all.
3 Yes and no. The bitrate ffects quality, but most AVI (like DivX and XviD) is heavily compressed.
In essence - Since every format conversion only can reduce quality, (and at a theoretically best possibly keep it) if possible avoid it.

/Mats

[redwudz]

If it's a DVD compliant MPEG-1 (Which a VCD would be, except for the audio), I would leave it as is. Re-encoding it, even to a higher bitrate will reduce quality through encoding losses. Just change the audio to 48K from the standard VCD 44.1Khz. Now if you need to change the video from PAL to NTSC or the reverse, you would need to re-encode, but that's about the only time.

Just about any video file is compressed, AVI included. A AVI type file like a Xvid may be 20:1 or higher compression. Of course 'AVI' is not really a description of a format, it's just a container name. DV, Xvids, Uncompressed video and quite a few others could be defined that way. MPEG-4 is a little closer definition, but it's also a container name. The best way to define a video format is by the codecs used for the video and audio. But probably more than you wanted to know.

The bitrate would affect re-encoding in this case as you are changing the format. A MPEG-2 encoded at 1000kbps will look terrible, but a Xvid at the same bitrate will look quite good. Very generally, you will have to re-encode a Xvid or similar with about 3 - 4 times the original bitrate when you convert to MPEG-2. The filesize will also increase proportionately. Say from 700MB for a Xvid to about 1500 - 2500MB for a MPEG-2 to maintain the same quality.

The relationship between bitrate and file size is simple. Bitrate X running time = size. We have bitrate calculators in our 'Tools' section that you can use to fit a AVI type file to a desired size when encoded to a different format.

You can get more information about MPEG formats to the upper left in 'WHAT IS' DVD, VCD, etc.

Hopefully, I don't have any typos in all that above, if so, someone should jump in with better info.

And welcome to our forums.

[thecoalman]

Is there any advantage to increasing the dvd bitrate above 1150?

No, that will in fact make it worse. It probably won't be noticeable but any conversion degrades video. It is what it is and adding bitrate won't help. Note that VCD video usues a 44khz audio, this does have to be converted for DVD playback.

I'm assuming the bitrate does affect the quality because an avi file has no compression. Is this correct?

AVI is just a container file that can contain many types of video from uncompressed which creates enormous files to Divx which will have file sizes similar to your MPEG1's . Divx however compresses very well at low bitrates compared to MPEG1 .

In regards to compressing a lightly compressed or uncompressed AVI when compressing to MPEG2 some loss in quality is to be expected, keeping it in the 6000-8000kbps range will will not be very noticeable at all. The lower you go the worse it gets but you also get smaller file sizes. Bear in mind there is also threshholds for the resolutions, 720x480 for example works well between 4000-8000kbps . Once you go lower than 400 or even want to use 4000 you should drop resolution. There's a lot of factors, the quality of the source being the most relevant and what will give you the best results can be gained from some testing and experience.

In regards to compressing a Divx when compressing to MPEG2, Divx bitrates are typically 1/4 that of MPEG so you would have to actually increase the bitrate about 4x to maintain quality.

EDIT: You guys type to fast.