Panasonic's AVCHD video format: questions about quality, compatability, conversion

Question

I've just bought a Panasonic Lumix TZ25 to replace my sadly defunct Lumix TZ3. This new camera is excellent, but I'm a bit confused over the video recording formats available. The user manual states:

This unit can record motion pictures in either AVCHD or MP4 formats... AVCHD records high definition quality images suitable for viewing on a large format TV or for saving to disc. MP4 is a simpler format best used when extensive editing is needed.

1. Is AVCHD superior to MP4? The way Panasonic describes it, that's the impression given. Yet surely MP4 can provide the same high quality?

2. Can an AVCHD video be shown on an Android tablet? My wife has an Asus Transformer and would is trying to view some holiday recordings on it but so far without any success - we're assuming there's a compatability problem?

3. Assuming that AVCHD is superior to anything else, is there any software out there which would convert AVCHD to a more widely used format but without discernible loss of image quality?

Answer 1

The AVCHD vs. MP4 is just a choice of a container format. When all other parameters are the same, choosing AVCHD or MP4 depends on the use you intend to give to the movie clips that you record. If you plan on doing editing, then MP4 is better because it has the index tables that video editors need to find frames fast using random access. If on the other side you plan to just streaming these clips over to a TV or computer then AVCHD is best as it is a transport stream, so players will have to do less work to play the clip from start to end.

Note that a utility like ffmpeg can easily convert between AVCHD and MP4 without any loss of quality, so really the choice you make isn't irreversible.

What determines image quality is the picture size and the recording bitrate, not the container format. I went to the site that has the specs for your camera and found it offers the following recording options:

• [HD Video]
  • 1920 x 1080 pixels, 50i (FSH: 17Mbps / AVCHD) (Sensor output is 25p)
  • 1280 x 720 pixels, 50p (SH: 17Mbps / AVCHD) (Sensor output is 25p)
  • 1920 x 1080 pixels, 25 fps (FHD: 20Mbps / MP4)
  • 1280 x 720 pixels, 25 fps (HD: 10Mbps / MP4)
• [STD Video]
  • 640 x 480 pixels, 25 fps (VGA: 4Mbps / MP4)

So for best quality you should pick the largest picture size at the largest bitrate. Looking at the above list the best choice is the FHD format, which is 1920x1080 at 20Mbps, and that option is only available in MP4.

The second and third options are at 17Mbps. At that level you have two options, 1920x1080 and 1280x720, both recorded in AVCHD.

Note that I'm not including frame rate in my decisions, since it appears the sensor in this camera can only record 25p.