Friday 9 May 2014

BirdBoxPiCam2014: two chicks & video quality

It must be a bit unpleasant sharing the nest with eight dead siblings.

But the two remaining great tit chicks seem to be doing OK, with mum making frequent visits to the nest to feed them and keep the place tidy.

There are now more flies buzzing around inside the nest, and I've noticed
mum remove small maggot like creatures a few times today.

In the nest

Things seem to have settled down in the last couple of days. The two remaining chicks look healthy and lively, and continue to grow at an alarming rate.

The feed rate appeared to be slowly dropping, day-on-day, but yesterday the female picked up the pace once again, and today is looking pretty good so far.

Several times today I've noticed the female root around in the nest and pick up little grubs or maggots. She seems to take these out of the nest, but once or twice she has returned a few minutes later with a very similar looking creature to feed the chicks. Maybe she processes these in some way before serving them up as lunch!

I've also seen the chicks carefully cleaning their wing feathers before trying them out by flapping vigorously. According to my calculations they can only be a few days away from leaving the nest (...Note: Sunday or Wednesday would be good for me. Any other day and I'll certainly miss their maiden flight!).

Video quality

I also found some time today to play with video quality. More specifically I've been changing bit rate and encoding options.

Most of the video recorded so far has been 640x480, 30fps, with a bit rate of 500kb/s.

So I've increased the resolution to 800x600 and varied the bit rate up to 2Mb/s. Clearly, as the bit rate goes up, so does the image quality. However the file size also increases.

As an example, a 5 minute video clip at 2Mb/s creates a 72.7MiB file. This is not huge, although I wouldn't want to upload anything this big to my blog.

To edit and create a short video clip from this size file for uploading, I cut and encode on Avidemux using the MPEG-4 AVC option (and default configuration settings) with an MP4 container format.

This will give me a 2MB file for a 30 second video clip. I can also play around with the MPEG-4 AVC config settings (not that I know what I'm doing!).

An option that looks useful is called "Encoding Mode" and by setting it to "2 pass - video size" I can determine the resultant file size.

Being able to set the output file size means I can choose a sensible size to upload (say 8MB). So instead of using a 2MB file, I can "upgrade" to 8MB and benefit from better quality.

However, as mentioned before, the video quality is degraded when uploaded to this blog.

This difference in quality between what I can see locally (pre-upload) and what appears on the blog (post-upload) is best illustrated by the captions on this video...they are perfectly clear on the local copy of this video, but rather hairy on the blog.

No comments:

Post a Comment