Practical Screen-craft - 1st December

Tuesday 1st December 2015 

Course Module - BAFI101                         Practical Screen-craft                    Lecture - Stu Bailey 

CODECS/Bitrate/Chroma-sampling/colours/compression/frame rate

At the start of todays lesson, Stu went over the piece of work that he had set us last week to do, based around Codecs, Bitrates, Chroma-sampling, he used the lesson to go through the questions we were asked and to give a deep analysis on certain aspects i.e. different codecs, their uses etc. 

Codec is an algorithm - Compression and Decompression 

Real important to use a codec to make images more manageable

All digital format use a codec 

A codec trades off image quality for file size

Balance between image Quality and File Size 

RAW - Known as uncompressed - 40MB

JPG - CODEC - 4MB

CODEC used in a 600D - H.264 (variations for the codec vary which is called Open Source) Re-work it to suit their needs. AVC CAM, AVC HD etc. It has become the go too codec, it gives very good image quality! 

Pretty much all DSLR's will record to H.264 - Can fit much more footage onto the card - seen as an advantage- 

H.264 IS OPEN SOURCE, H.264 CONTAINER IS MP4 

The newest version is H.265 (supports 4K) 1GB - H.264, H.265 - 100MB - will become the new replacement.


Another CODEC

Apple Pro Res - (Professional Resolution) is INTERMEDIARY - Within the pro res there is a family - lots of different versions.      

CANNON XF100 will give you an approved CODEC - . records in .mxf - MPEG-2 open sourced by cannon for their consumers.

CINEFORM - High end codec that is used by Go Pro but it doesn't have to be used for Go Pro.

If there is a film that is going to be extensive, steer away from shooting on H.264 - you could light up the film on camera with lighting equipment and shoot it the way you want to - You could get away with using H.264, however the colours wouldn't be vivid. 

Convert video - Transcode from on codec to another 

EXAMPLE - PRO RES ---- CINEFORM (Putting our film in a better container so we can do more and get more out of it, great for colour correction.

DVD - MGEG-2

Anything for streaming or for use on the web - H.264 - Codec's need to define video compression 

Bitrate - Decreasing the bit rate would decrease the overall size and quality of the image. Variable bit rate is good to use for motion. 

COLOUR - Chroma Subsampling 4:4:4 - used for red camera's like the alexia, doesn't chuck much colour away. broadcast colour system we use for PAL is 4:2:0. Were aiming for a suitable colour of 4:2:2.

Colour Bits ^ Amount of colours 8 bit/10/12/14   H.264 (4:2:0) 8 bit (28)

Pro Res (4:2:2) 10 bit (210)

RESOLOUTION - SD HD 4K 8K

FRAME RATE - 24/25/30 - FLASH VIDEO 15

COMPRESSION - INTERFRAME / INTRAFRAME - COMPRESS A GROUP OF FRAMES OR A SINGLE FRAME AND COMPRESSES IT, TAKES THE COMPRESSION FROM THE FIRST FRAME AND WILL GUESS THE DIFFERENCES BETWEEN EACH FRAME, ALL IT WILL STORE IS THE DIFFERENCES BETWEEN MOTION AND LIGHT, NOT THE COLOUR AS THAT WAS DONE IN THE FIRST FRAME.

^^^ Group of Pictures ------ USUALLY ABOUT HALF A SECOND 11-13 FRAMES