Effect of TMPGEnc motion search precision with CBR encoding

[huykin]

Does the TMPGEnc setting of "Motion search precision" affect the quality of constant bitrate encoding (MPEG1/MPEG2)? It certainly affects the encoding time: the time approximately doubles when I switch from Normal to High Quality, and then doubles again when I go from High Quality to Highest Qaulity.

The TMPGEnc help says: "Motion Search Precision - Set how to search the movie so that the most appropriate bitrate can be found. A higher bitrate is required for scenes with much motion, and this sets how TMPGEnc will search for these motion intensive scenes if variable bitrates are to be used." So this looks like it should affect only VBR encoding. But then why does the encoding time change so much with CBR?

If MSP does affect the quality with CBR, is Highest Quality an overkill? In other words, was anybody able to see an improvement in going from High Quality to Highest Quality?

Thanks.

[i-on-s]

I usually put it on Normal...i havent seen any diff between a clip put on normal than put on highest....so just use normal and i have no clue why time doubles on CBR i usually encode using CQ or VBR myself.

[adam]

Yes this setting will still affect quality for CBR encoding. The reason is that VBR or CBR only sets how much bitrate gets allocated every second, but the motion search precision sets how that bitrate is distributed per frame within each second. So even with the same amount of bitrate every second you can still get better or worse quality depending on how well those bits are distributed to each frame.

By increasing the motion search precision setting you are telling TMPGenc to search much more dilligently to find the motion changes. The idea is that the more it finds out about your source in this regard, the better it can allocate that bitrate. Of course this comes at a cost of encoding time.

Regardless of whether you are using CBR or VBR the general consensus is that highest quality will only produce marginally better results than High quality and it comes at a huge price in encoding speed. I think the author of TMPGenc has even said that this setting is probably overkill.

So generally my advice is to use High quality if you can take it or else Normal.

[Xtasy2002]

I use high motion and the previous poster was right, it makes a big difference even with CBR. I used to use normal on this setting but I noticed a ton of Macroblocks in all of my encoded mpg's. Setting it to high all but eliminated these blocks and the scenes are much smoother now.

[huykin]

Thanks a lot, people! That's exactly what I needed to know.