Not all AVCHD files are created equal

What source are the .m2ts files from? Have they been converted or copied onto the pc?

Hi pjc,
Thanks for your swift reply.

The m2ts have been copied onto my PC directly from my camcorder (Canon HG10). No conversion or modification has been done before adding them to a project in PowerDirector.

I can't really understand what's happening behind the scenes; producing an mpeg-2 file from an "untouched" m2ts" file shouldn't generate a significantly larger file compared to the original. I hope I'm right in this thinking!

I have also put together a movie consisting of approx 1.5 GB of m2ts files. Upon production, the resulting mpeg-2 file becomes approx 3.5 GB big.

Looking forward to further assistance/hints.
Again, many thanks for responding. Much appreciated.

Best regards,
Pontus

If you are converting to mpeg2 then you will get a larger file size as AVCHD is more compressed than mpeg2. If you render as an AVCHD file does the file size change greatly?

edit: I wonder if you are thinking the .MTS or .m2ts files are mpeg2 encoded? They are in fact mpeg4 AVCHD in a transport stream container.

Have a read of this thread. http://forum.cyberlink.com/forum/posts/list/4312.page#16518

Also use the search and type "AVCHD" and have a read about problems people are having.

Thanks for clarifying that AVCHD is MPEG4, I read somewhere that they are MPEG2.

I did an experiment with rendering a M2TS file from my Canon HG10 (1920x1080i) in PowerDirector with the parameters File / AVC .MPEG4 / Quality AVCHD 1920x1080.

The size of the produced file became 27MB compared to the original 12 MB, i.e. still more than double the size.

I'm still a bit confused as to why the size increases that much.

Any further help you can provide in helping me understand is mostly welcome. Many thanks.

Regards,
Pontus

Pontus,

What recording mode was the orignal clip recorded at on your HG10. I think the default is SP 7Mbps for that camera.
HXP, 15Mbps
XP, 9Mbps
SP, 7Mbps
LP, 5Mbps
How does this compare with the bitrate in the profile you are using?

Jeff

Hi Jeff,
Thanks for your reply!

The recording mode was HXP, 15 MBPS.

The Rate control setting in the default setting in the rendition seems to be CVBR, average bitrate 14800 kbps and max bitrate 20000 kbps. So there seems to be a good fit. Do you know if PD selects the rate control by checking the file(s) about to be rendered, or is it a completely manual process?

POntus

Pontus,

I'm not sure I agree. In talks with a Canon rep here about 1 yr ago he indicated that 15Mbps was the maximum bitrate for the HG10 and Canon uses VBR so the amount of record time varies depending on scene changes. Makes sense from sales approach, claim highest capability. He did not have an average bitrate. Average bitrate is very important on file size and size also very dependant on scene changes with VBR. Shoot some tripod footage at a static object to get a feel for significance.

If you are "producing" a file I think you are totally in control of selecting a default profile or modifying and creating your own profile. PD does not do it automatically. I don't see where you get the max bitrate of 20000Kbps in a default profile unless you have modified one.

I don't know how much of the file size difference you are seeing is real or just a false attempt on mimicking the HG10 record mode. Very interesting though, based on everything posted, I'm not sure how well AVCHD has been shaken down.

Jeff

Hi Jeff,

Thanks a lot for sharing your knowledge with me. It really makes sense what you are saying - the stated bitrate of 15 Mbps is probably the maximum bitrate and surely not the average one.

I'll do some further experimenting by lowering the average bitrate setting upon production.

There is an option in PD where you can select constrained VBR (CVBR) or just VBR. What would in your opinion make most sense to use when producing a file (from AVCHD as in my situation)?

Thanks again - I will post my findings after experimenting with different bitrate settings.

Pontus