[IPOL discuss] Video demos: request for comments

[Miguel Colom]

Dear all,

The IPOL team is working on adding video data as a native type in  
IPOL. It'll allow user to directly upload video files to the demos.

The system will allow two kind of conversion for the videos:
a) The input video will be converted with the HuffYUV codec. This is a  
lossless codec which simply uses Huffman compression to reduce the  
size of the final file. The algorithm will be provided with one (or  
several) video files within an AVI container.

b) For those authors who prefer to handle the video simply as a bunch  
of PNG files, we'll provide also this option. For example, if the  
users configured that they wanted to read 30 frames from the video,  
their problem will find files with the name input0_frame000000.png,  
input0_frame000001.png, ...  input0_frame000029.png.

The users can choose which option fits best their needs.

In the DDL it'll be possible to specify these options:
- To convert the video to an uncompressed AVI or to a bunch of PNG files
- The maximum number of frames the user wants to process. The system  
will read this number of frames reading them from the middle of the  
input video.
- Optionally, the maximum size of the frames. The system will zoom-out  
the frames if they're bigger that this maximum. Only if this is  
specified.
- Optionally, if the video frames should be converted to grayscale.
- The color space (RGB or YUV).

This is still a work in progress, and that's why we're presenting it  
here, to know if everybody agrees with this, or if you have any  
suggestions or remarks.

About the presentation of the results, the browsers are only capable  
to show MPEG4-encoded (.mp4) videos. Unfortunately, MPEG4 videos are  
compressed.
While this is not a problem for some applications (say, stabilization,  
object detection, color processing), it's not good for enhancement  
algorithms such as denoising.

We'd recommend to present the results as a MPEG4 video when the  
presence of compression artifacts are not a problem for the  
application, but to show individual frames in a gallery otherwise.
We'll provide a script that you can call easily from your demoExtras  
scripts to produce videos that you can view on the browsers, as well  
as at least one example demo that you can copy from as a stencil to  
create others.

Best,
Miguel