MPEG1 custom GOP settings

[sipposa]

I have a need to encode MPEG1 video with these settings:

MPG1
720x576 pixelratio 0.7031 (16:9) 25fps
constat bitrate under 2mbps

GOP-settings
M-frames 3
N-frames 15

Hard part seems to be GOP settings since I cannot find free software which allows me to set those. I really need to have settings like that since the hardware player won't accept anything else. I know Adobe Premiere can do this, but it is too expensive and cabable for my purposes since I only need to convert videos.

[Cornucopia]

TMPGEnc? bbMPEG? QuEnc? Mainconcept? Procoder?

The "M" number is the distance between anchor frames, the "N" number is the distance between I frames. So what this is telling you is that you need a GOP structure that looks like this:

IBBPBBPBBPBBPBB,I...

This is a VERY common sequence so you shouldn't have any trouble getting most, if not ALL, MPEG1 encoders to do it.

Scott

[Computer Nerd Kev]

How about that.
Two newbies, you and me, both making their debut with a quite similar question.

From what I've learnt through that, I propose the following ffMPEG CLI arguments to suit your situation:

-f mpeg1video -g 15 -bf 2 -flags2 sgop -r 25 -s 720x576 
-aspect 0.7031 -bufsize 83886080 -b 1992294.4 -minrate 1992294.4 
-maxrate 1992294.4 -bt 79692

This will not give you true constant bitrate because this does no seem to be do-able in ffMPEG, but it may get it close enough to do what you want.

I should also point out that I have simply given a bitrate of 1.9Mb/s here (thus under 2Mb/s), if you want a different bitrate, simply replace the areas with the number 1992294.4 with your preferred bitrate in bits (or in kilobits with "k" at the end). If you do this, you will also need to divide your new bitrate (in bits) by your framerate, and replace the numbers after "-bt" with the resulting number.

Of course, you can probably use some of the programs listed by Cornucopia, which have GUIs, but this is just another option.

[sipposa]

Thanks for your replies but I need to get those GOP settings match perfectly or else the video won't work.

So if this is very common sequence, what program will do that and what is the configuration? Since mony programs I have looked don't let me define M= and N=, or that actual I, P, B frame structure.

[El Heggunte]

I have a need to encode MPEG1 video with these settings:

MPG1
720x576 pixelratio 0.7031 (16:9) 25fps
constat bitrate under 2mbps

2Mbps in MPEG-1 is good enough for VCD resolutions and framerates only. A Full D-1 PAL video in MPEG-1 most probably would require bitrates above 10Mbps Not to mention that the olde and goode TMPGenc Plus is the only application (AFAIK) that was optimized for MPEG-1 compression beyond the VCD requirements.

[Computer Nerd Kev]

Those command line arguements should give you the correct GOP structure from ffMPEG. However if you would rather use TMPEGEnc for this, simply click on the "setting" button and enter your required settings under the video tab. After this, go to the GOP structure tab and matching your settings to this screenshot should give you the GOP structure you require.


[Attachment 7775 - Click to enlarge]

[sipposa]

Those command line arguements should give you the correct GOP structure from ffMPEG. However if you would rather use TMPEGEnc for this, simply click on the "setting" button and enter your required settings under the video tab. After this, go to the GOP structure tab and matching your settings to this screenshot should give you the GOP structure you require.


[Attachment 7775 - Click to enlarge]

Thanks, but seems that your attachment is not working:

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[jagabo]

Thanks for your replies but I need to get those GOP settings match perfectly or else the video won't work.

So if this is very common sequence, what program will do that and what is the configuration?

Cornucopia already answered that.

[Computer Nerd Kev]

Those command line arguements should give you the correct GOP structure from ffMPEG. However if you would rather use TMPEGEnc for this, simply click on the "setting" button and enter your required settings under the video tab. After this, go to the GOP structure tab and matching your settings to this screenshot should give you the GOP structure you require.

Thanks, but seems that your attachment is not working:

vBulletin Message

Invalid Attachment specified. If you followed a valid link, please notify the administrator

Looks like its back to the old fashioned way then.

Under the GOP structure tab:

Number of I picture in GOP: 1
Number of P picture in GOP: 4
Number of B picture in GOP: 2

Output Interval of sequence header: 1 GOP
MAX number of frames in a GOP: 15

The tick boxes at the bottom specify other modifications to the GOP. Not knowing what you intend to use the outputted video for, I can not recommend settings for these. However if you are having trouble, I would recommend leaving them all off.