FFMPEGX changing Bitrate ut always get the same result

[earlygrace]

Ok, is it just me, am I a moron? But everytime I set the Bitrate in FFMPEGX I get the same size file at the end. I rip a M2V file from a DVD, say it is about 6Gb then

If I set it to 4000 I get a 2.5gb file,
If I set it to 8000 I get a 2.5gb file.

Am I doing somthing wrong? All I want to do is produce a file small enough to fit on a DVD-R but not to small, cause I don't want to loss to much info. Don't even suggest Fotry-two, as the results are always a jerky video and out of sync audio, plus I can only get an ISO.image no streams.

[earlygrace]

So I guess there is no way to control the video bitrate when converting mpeg2 to mpeg2 with FFMPEGX

So what I type within the Bitrate Calculator is compleatly ignored, or it seems to be. Then tell me what the hell is the point having the Bitrate Calculator if the results are not applied to the files!

Getting frustrated

[schmeg]

Are you using the Quicktime decode option for your MPEG2 files?

When you view the resulting m2v, does it contain the whole length of your movie, or just the first part?

If so, be aware that Quicktime has a 4 GB file limit. This is relevent to your source file -- if it's over 4 GB, ffmpegX/QT decode may be "locking up" at a certain point in the decode process. This happens often, for example, if you load a VOB into Quicktime Pro. A two-hour movie may appear to only be 18 minutes long, and it'll freeze on a still frame 18 minutes in.

Solution: split your MPEG into chunks smaller than 4 GB, and then try it.

Or first try just one chapter, or a little "extras" file just to see if it works.


If you're not using the QT decode, then give us some more details about your other settings and the source file.

[major]

If you're encoding to SVCD, the bitrate is locked to 2500 as required by the standard, and you need to choose "XSVCD" profile to unlock it.

[jefwest]

You're not just a moron earlygrace, these bitrate calculators are a load of shit it seems. I mean, I put in my info, they tell me like 3000 kbits, so i use that, figuring on getting like exactly 4.36 GB, instead I'm stuck with 2 GB, it's like I could put another fricking movie on the same dvd-R if i am gonna go that low on size? How do you just get a 6.7 GB .m2v/.ac3, or .vob, to a DVD that will play in a player and allow you to fastforward/skip to parts? I am still lost, I know DSP is the way, but I can't work that it's much to complex or I'm just a moron but I can't get it to build me a damn image. Anyways, Now I have a .m2v and a .ac3 of braveheart, a large movie, and I want to re-encode at smaller size, just small enough to fit on a DVD-R, anyone got any suggestions? I'm trying minx when i get home.....should I automatically select 3:2 Pulldown as well? I don't really udnerstand that option, I know it's use for NTSC "FILMS", but are DVD's considered FILM Sources? Just curious!

West

[major]

these bitrate calculators are a load of shit it seems

No, the calculators give the right answer for perfect CBR streams, however when you encode in variable bitrate mode (VBR) there is no mathematical way of predicting the final size, as the bitrate will vary without notice depending on the content of your source material (complex motion, etc). So the issue is not in the calculator, but in the bitrate control system of each specific codec and the choice of CBR vs VBR mode.

[timbo22]

Major,
Technically things should work the way you say. However, both 42 and ffmpegx (using mpeg2enc) seem screwed up in this respect. If you trying encoding the same movie at VBR 5, bit rate 5000, you often get the same size output as VBR 5, bit rate 8000. This clearly should not be. Infact it seems like no matter what you set the bit rate to, the file comes out to a certain size for each VBR setting.

While we're on the subject of being annoyed with mpeg2enc, why cant mpeg2enc use a multiple pass method and encode VBR with an AVERAGE bit rate darnit! Would make calculating output size really easy with the quality advantages of VBR.

[major]

mpeg2enc has no multiple pass capability for now. So if you want to increase the filesize for your 8000-bitrate file, you should either lower the q value or use CBR.

[timbo22]

Major,
Am i wrong or is it a bug that mpeg2enc produces the same size file when encoding at VBRQ 5, bit rate 3000 and VBRQ 5 bit rate 8000?

[major]

I would not call it a bug, as when encoding VBR the bitrate value is meant as the -maximum- allowed bitrate, so probably your source matierial doesn't need a bitrate increase to fit q=5.

[smurf]

i think i know what you have forgotten, i HAD the same problem,

you have to change, so you vreate a NONstandrard mpeg file

this is maybe alrdy said, , i did not want to read all, just help,

GG smurf

[hikaru124]

mpeg2enc has no multiple pass capability for now. So if you want to increase the filesize for your 8000-bitrate file, you should either lower the q value or use CBR.

does ffmpegX recognize alternate qvalues? I've played (albiet with short clips, 3-4 minutes) around with q and generated same results regardless of the setting. i've also found that sometimes ffmpegX doesn't seem to recognize cbr being set.

is there anyway to reintroduce the 'show the command line' option? look at what commands are being used to trace/figure out ffmpegx is calling & how? or be able to edit command lines and specify our own parameters (ie: the -H/-h quality thing being broken in .8, etc)?

thanks!