Saturday, April 16, 2011

tablet video resolution - 640x480 for less than 10 inch

HD video, how fantastic?

Well actually for a lot of devices it is overkill.

As the Digital Camera market became cannibalised by Camera phones, their answer was to keep upping the resolution.

So now we have compact* Digital Cameras that take photographs in 720p and 1080p

(*I can see the point for SLR type "Professional" specification cameras, to do extremely high resolutions like 1920x1280, but for compacts that live in pockets and handbags ... err no. )

  • OpenShot: 'Web' -> 'Youtube' -> 'Square NTSC' -> 'High'
     [ above gives okay 640x480 at video bitrate 8 Mb/s ]
  • OpenShot: 'Web' -> 'Youtube' -> 'Square NTSC' -> 'Med'
     [ above gives okay 640x480 at video bitrate 5 Mb/s ]
  • OpenShot: 'All Formats' -> 'Mpeg2' -> 'Square NTSC' -> 'Med'
     [ above gives okay 640x480 at video bitrate 5 Mb/s ]
  • OpenShot: 'All Formats' -> 'Mpeg2' -> 'Square NTSC' -> 'High'
    [ above gives okay 640x480 video bitrate 15 Mb/s ]
The four options above give output that looks great on the Archos 5 internet tablet.

( I emphasized the 'Med' options as they are what I would normally use - a reasonable balance between quality and filesize. The last option which uses video bitrate 15Mb/s might be useful for larger tablets or if you view you videos on a large resolution monitor )

In OpenShot the menu File -> Export Video    will bring up a dialogue box, with two tabs 'Simple' and 'Advanced'

The 'Simple' tab has boxes for 'Project Type', 'Target', 'Video Profile', and 'Quality', which should be set to the values in the bulleted list above.

There should be no need to consult the Advanced tab, but I give an illustration here for those who want even finer grained control over the output:



Mpeg2 - why not Mp4 or H264?

Quite simply, Mpeg2 produces good quality, compact, video that looks great on a 5 inch tablet.

H264 / Mp4 are codecs I have looked at also, however they did not seem to offer either (i) smaller file size (after encoding), or (ii) better presentation results (looked the same to me)

( Having read about the Free Software Campaigns MPEG-LA boycott, perhaps I can do a little, by not advocating their newest video standard, and including a banner )

Newer android tablets have WebM support, and OpenShot includes WebM support on newer GNU / Linux installations.


Links and Further Reading:

The Archos 5 tablet is a capable Android tablet, although I do not own one personally.
( I do help out other folks convert their high resolution videos for use on their own Archos 5 inch tablet though. )

If you are really short of file space, then it is possible to manually adjust all 4 of the options in the first paragraph downward to use 1 Mb/s, however the quality reduction will be quite noticeable.

    4 comments:

    Gary said...

    If you really must use a different format and think xvid might be a better fit, then you might see OpenShot complain 'missing libxvid'

    The obvious thing might be to install libxvidcore4

    On Ubuntu Lucid you might also try installing either or both of the following:

    gstreamer0.10-plugins-bad-multiverse

    ogmrip

    and see if the libxvid not found complaint goes away.

    Gary said...

    With WebM being the preferred video codec in Firefox and Chrome, the options I listed saying 'youtube', may well change in the future to give WebM output.

    http://www.webmproject.org/about/supporters/

    There is no issue really, as the two later options (from the 4 listed) give the 'All Formats' way of specifying Mpeg output :)

    Gary said...

    If you find the 576p, 720p, 1080p thing a little confusing then the following site:

    http://www.whichtv.com.au

    ...can help give you some idea about how 640x480 or higher might compare with the resolution on a full sized standard TV set.

    Most TV sets are over 20 inches, which explains why the broadcast is usually at a much higher resolution, than say what you would need for a 5 inch tablet!

    Gary said...

    File sizes are something which you might want to consider if you are using a device which has limited internal memory (8GB fixed) and no expansion.

    An Archos 7" 8GB can be expanded, but you might want to be frugal with the internal memory.

    Using Web->Youtube->Square NTSC->Med makes a 30 second movie clip (MVI_0746runChallengeQual5mbps) have a filesize of around 18 meg.

    Reducing the video bitrate to 1mbps will get that 30 second clip down to 6 meg filesize, however the quality will be so low that it will only be acceptable on 5 inch tablets or smartphones.