Question for Bob Regarding File Types

[George Tyndall]

Hi Bob,

I’ve just noticed that, when I Share/Output my PREL file on PRE7's 1920 x 1080 timeline to Personal Computer as an HD MPEG2 1920 x 1080 30 file using the machine in my signature, it shows up as an m2t file on my external HDD, however, when I output that very same PREL file on a machine that has Win7 for an OS, it shows as an AVCHD file.

When you have time, please enlighten me with regard to the difference(s), including the difference between an m2t and a MPEG2 file.

Thank you.

[Chris B]

I'm not Bob - but my brother is....

The worst thing windows ever did was hiding the file types. An extension to the filename is a just a name. Windows interprets these to be "helpful" - sometimes it's not. Renaming a file will make windows think it's something else but it makes no difference to the files content.

M2T files output by Elements are "transport stream" MPEG files. (also named .TS, TP or MPEG-TSsometimes). "normal" mpeg files (.mpg .mpeg .mpeg2) are "Program Stream". Basically transport stream is designed for broadcast whereas program stream is designed for DVDs. More detail here : http://en.wikipedia.org/wiki/MPEG_transport_stream & http://en.wikipedia.org/wiki/MPEG_program_stream

AVIDeMux (http://fixounet.free.fr/avidemux/) will convert one to the other.

[Paul LS]

Not sure I understand George. What do you mean by with Win7 it shows as an AVCHD file? Do you mean it exports it with a .mts/.m2ts AVCHD file extension? Exporting HD MPEG2 from PE on any OS system should still export it as a MPEG2 file type.

[Bob]

Hi George,

When you say it shows up as an AVCHD file on Windows 7, are you referring to the AVCHD video label that appears when you hover the cursor over the file name in the Windows Explorer (AVCHD video also appears in the properties detail tab). If so, ignore it. I noticed that in my Windows 7 system too. Windows is simply displaying predefined text and someone called m2t files avchd video. As long as you are using the same mpeg2 preset to share your HDV project, you'll get an m2t mpeg2 file -- same as under XP.

M2T refers to the container format. The container format defines how video and audio streams are stored in the file. As Chris points out, m2t containers use a transport stream format. But, the container format does not define the contents of the streams. The streams themselves are defined by the codec used to encode them. HDV uses mpeg-2 to encode the video stream.

Contrast that with AVCHD. AVCHD also uses transport stream container files. However, the file suffix used is M2TS. And, AVCHD encodes the video stream using H.264/MPEG-4 AVC.