question about mpeg 2 format

matrix man · Post by **matrix man** » Sat Nov 26, 2005 2:35 pm

hello everybody,
I live in a pal country and i want to adjust my mpeg 2 properties of creating a video files to the best quilty so what are the properties i should use and what these options " two pass endcoe" and "l-frames only" mean
in the video setting?
thanks a lot

skier-hughes · Post by **skier-hughes** » Sat Nov 26, 2005 6:00 pm

Max bitrate of no more than 8,000.
Make the normal setting no less than 1,000 less than the max, when using vbr.
Minimum can be 0.

Now, what your max is will depend on the length of video you have, with under an hour you can max it at 8,000, but if you have an 1 1/4 you may struggle to get it ona dvd, unless you use ac-3 audio, an 1 1/2 and you'd need to lower the max bitrate.

VBR (variable bit rate)or two pass takes two passes to encode the video, it looks at it to see what encode settings to apply to each frame and then does it, varying the bitrate depending on the content of the frames, more movement higher bitrate.

CBR is constant is a set bitrate, but even this is not constant as it is only a mean average depending on the gop settings made, so each of say 15 frames has the same bitrate, but the next 15 may have a different bitrate.

i frames only is a bit like an avi, as you get i, b and p frames in a gop with mpegs. An i frame is the only real frame, to get the compression you then have made up frames inbetween each i frame. The further apart the i frames the smaller the video, the poorer the quality.

rguthrie · Post by **rguthrie** » Sat Nov 26, 2005 6:16 pm

According to the user manual:

I-frames only: By selecting this option, the MPEG encoder
will only compress the video to something called I-frames
(and not P or B frames). This makes the quality better but the
file size will be much larger. For most people, you should leave
this option unselected, as it disables an important part of
MPEG compression.

Two-pass encode: Select to analyzes the video stream
during the first pass to pre-determine the most appropriate
compression for each frame. This video encoding method
adjusts the bit rates more efficiently to create better,
smoother visual quality.

Hope this helps,
Ron

NOTE: If you use two-pass encode expect encoding to take a long time.

matrix man · Post by **matrix man** » Sun Nov 27, 2005 6:49 pm

thanks a lot, I burned the movie according to to this properties:
PAL (25 fps)
MPEG files
24 Bits, 720 x 576, 25 fps
Lower Field First
(MPEG-2), 4:3
Video data rate: Variable (Max. 8000 kbps)
Audio data rate: 224 kbps
MPEG audio layer 2, 48 KHz, Stereo

and the quilty of the movie is great but i have a different problem now which is "no sound".
i don't hear the movie

rguthrie · Post by **rguthrie** » Sun Nov 27, 2005 10:24 pm

Hmm, that's interesting. I usually use Dolby Digital for audio since it has a better compression rate than MPEG audio. Maybe someone else can help you better here.

Ron

matrix man · Post by **matrix man** » Mon Nov 28, 2005 1:17 pm

and the strange thing is that there is sound when i hear it through the computer

skier-hughes · Post by **skier-hughes** » Mon Nov 28, 2005 6:59 pm

mpeg sound is the least compatible with dvd players, so either use pcm if you have the space or preferably AC3 if you have that option. This is most compatible and also gives the smallest file.

THoff · Post by **THoff** » Mon Nov 28, 2005 8:48 pm

I frames are Independent frames, i.e. those that are not incrementally compressed by describing the differences from the preceeding frame. Essentially, each frame will be a complete frame, which is why the compression ratio will be so much worse.

Two-pass VBR encoding will yield somewhat better quality at the expense of one extra pass needed for determining an optimal bitrate allocation for complex scenes or high-motion video segments.

MPEG audio support is required for PAL DVD players, but it is not required for NTSC players. So for PAL countries, it's a good choice, while for NTSC countries, it is a poor one.

skier-hughes · Post by **skier-hughes** » Tue Nov 29, 2005 3:33 pm

Living in PAL land I've found mpeg audio to be a poor choice here as well

matrix man · Post by **matrix man** » Tue Nov 29, 2005 5:30 pm

so what do u suggest?
and how can i choose something else besdies mpeg audio after i chose the mpeg 2 format?

THoff · Post by **THoff** » Tue Nov 29, 2005 9:41 pm

skier-hughes wrote:Living in PAL land I've found mpeg audio to be a poor choice here as well

MPEG audio support is REQUIRED for all PAL DVD players, because at least one of the audio tracks on all PAL DVDs must be in LPCM, Dolby Digital, or MPEG audio format. Additional audio tracks in other formats may be present, but this is not required.

matrix man · Post by **matrix man** » Tue Nov 29, 2005 9:58 pm

the problem is that i can't hear from the tv itself but only from my YAMAHA receiver

skier-hughes · Post by **skier-hughes** » Thu Dec 01, 2005 2:55 pm

THoff wrote:
skier-hughes wrote:Living in PAL land I've found mpeg audio to be a poor choice here as well
MPEG audio support is REQUIRED for all PAL DVD players, because at least one of the audio tracks on all PAL DVDs must be in LPCM, Dolby Digital, or MPEG audio format. Additional audio tracks in other formats may be present, but this is not required.

Maybe it works with pressed dvds, but in my vast experience of producing burned dvds I have found the pcm and ac-3 to always be compatible, and I'd use ac-3 out of choice for file size. I have had trouble with compatibility with mpeg audio on pal dvds.

matrix man · Post by **matrix man** » Fri Dec 02, 2005 3:58 pm

maybe i should change the audio type , audio frequency, and audio bit rate?

skier-hughes · Post by **skier-hughes** » Fri Dec 02, 2005 5:48 pm

You should be able to change the audio type when setting up the dvd, I would pick either pcm or AC3.

Keep your overall bitrate, Audio and video to below 8,000. So if audio is 224, set max for video to 7500, with a variable bitrate as well set the normal to no less than 1,000 below the max, with the minimum being 0.

Graham