x264 Interlace and MBAFF Encoding

[ron spencer]

Is it right that x264 cannot encode to an interlaced file but instead uses MBAFF? That is, if my camcorder inputs are TFF, I cannot explicitly make x264 encode to TFF despite having the TFF option set; it will use MBAFF for all interlaced encodes...is this correct?

[sneaker]

MBAFF is one of the ways to encode interlacing with H.264, it has nothing to do with the field order (tff/bff).

[ron spencer]

Sorry...I guess I was not thinking when I posted.

I have 1080i files from my camcorder. So:

1. When I encode them with Adobe's Media Encoder I have an option of using MBAFF or not. If not, I get output files that have the same scan order as my input, which is TFF. Again MBAFF is an option.

2. With MeGui, which uses x264, I can specify TFF for sure as the interlace, but there is no option to choose MBAFF.

So there must be something the Adobe encoder can do with the interlaced input that does not require anything special, whereas x264 will always use MBAFF (or PAFF if asked). Is this the case (x264 can only use MBAFF or PAFF to deal with interlacing) ?

[poisondeathray]

x264 cannot use PAFF, it only uses MBAFF

If you use --tff or --bff , it will use MBAFF ; otherwise it uses progressive encoding

[jagabo]

2. With MeGui, which uses x264, I can specify TFF for sure as the interlace, but there is no option to choose MBAFF.

You automatically get MBAFF if you specify --tff or --bff. x264 always uses MBAFF. MBAFF does not imply the field order. It's how the interlaced frames are handled internally -- macroblocks with combing are encoded interlaced, those without combing are encoded progressive. The output of the decoder is interlaced frames regardless of how they are handled internally.

[ron spencer]

OK that explains it....thanks all!!

[PuzZLeR]

Just for the record, the H.264 standard fully supports MBAFF/PAFF, however, as mentioned, x264 only uses MBAFF. This is why it's not an option (MBAFF or PAFF) since MBAFF is the only one you'll get when working with interlaced encoding wit x264, and, as mentioned, selecting TFF or BFF is another matter.

If you really need PAFF in H.264, you can use MainConcept. But, I do believe, MBAFF is more efficient anyway, and really all you'd need for most, if not all, source, including yours.