De nuevo gracias por la atención.
Estas son las opciones que veo que tiene mencoder referentes al GOP:
Sólo me ha quedado claro que en MPEG-1 (VCD) el GOP es 12 (max y min)
En MPEG-2 es 15 para PAL y 18 para NTSC
Se supone que se hace de forma automática, al seleccionar el tipo de salida. Es decir, al yo seleccionar en Kino que voy a sacar la grabación en MPEG-2 y PAL, se supone que mencoder me pone esos valores a 15.
El resto de comentarios no me han quedado muy claros.
Estas son las opciones que veo que tiene mencoder referentes al GOP:
Citar
-g|--min-gop-size num
-G|--max-gop-size num
These flags set the minimum and maximum group-of-picture (GOP) size for the output MPEG stream. The default values depend on the output format.
For MPEG-1 (for example VCD) the default is a fixed GOP size of 12 (-g and -G are both set to 12).
For MPEG-2 the default value of -G (max) is set according to the video system: -G 15 for 625 line (PAL) and 18 for 525 line (NTSC). If -g (min) has not been specified then the minimum GOP size is set to be one half of the maximum (-G).
To force a fixed GOP size specify both -g and -G with the same value.
If the minimum and maximum GOP sizes are not identical then mpeg2enc will start a new GOP if more than 60% of the macroblocks in a P or B frame are Intra encoded. This ensure big changes of image coincide with a fully-encoded I-frame by starting a new GOP. This can help prevent transient "blockiness".
Reasonable minimum GOP sizes are 6 or 9. If a minimum is not specified but a maximum is given then the minimum will be set to one half the maximum. A larger GOP size can help reduce the bitrate required for a given quality. However, this really only applies to high-quality source material with little noise (e.g. digital video). For broadcast material there is little point setting GOP size much beyond 21 or 24. Even with good source material diminishing returns set in quite rapidly. Also it must be noted that specific MPEG-2 formats (such as for DVD) are constrained in the maximum allowable GOP size.
Note: mpeg2enc is currently hard-wired to produce 2 B frames between each I/P frame unless the GOP size forces less. This is reasonable for medium to high bitrates (>= 1Mbps) but probably sub-optimal for low-bitrate encoding.
-c|--closed-GOPs
Setting this flag causes the encoder to generate only "closed" GOPs (Groups of Pictures) that can be decoded without reference to their predecessor. This is useful for streams that are supposed to be used in multi-angle DVD's and applications where more easily edittable MPEG is required.
Sólo me ha quedado claro que en MPEG-1 (VCD) el GOP es 12 (max y min)
En MPEG-2 es 15 para PAL y 18 para NTSC
Se supone que se hace de forma automática, al seleccionar el tipo de salida. Es decir, al yo seleccionar en Kino que voy a sacar la grabación en MPEG-2 y PAL, se supone que mencoder me pone esos valores a 15.
El resto de comentarios no me han quedado muy claros.