Video Compression Series (Pt.2)

Let’s talk about containers. When dealing with multimedia files, containers are used as a wrapper, holding many files together to make our lives easier. The container may hold several codecs for video and audio tracks as well as other data used to inform the operating system as to what program(s) can be used to decode. There are multimedia containers used only for audio, video, animation and still images, while other containers are more flexible and can contain several codecs. Some common examples of container formats are as follows…

Audio: AIFF, MOV, WAV, MP3, XMF, WMA

Video: AVI, MPEG, FLV, WMV, MKV, MOV, MP4, MFX, VOB

Images: TIFF, PNG, JPG, BMP, PICT

Learn more >>

Now on to the guts of the containers. Codec is a loosely used term to describe the file formats contained in the wrapper. More times than not, if someone talks about a codec they are referring to a compression format or standard. Codec stands for Coder Decoder and is a program which converts analog data to a digital data stream. A description from Wikipedia; “A codec encodes a data stream or signal for transmission, storage or encryption, or decodes it for playback or editing.”. The following are some common codecs (formats) found in multimedia containers…

Audio: AIFF, AAC, PCM, MPEG-4, AC3

Video: HuffYUV, FFmpeg, H.264, ProRes, WebM, x264

Learn more >>

Now on to transcoding. Transcoding is the act of converting one file type to another. The process can change the container as well as the codecs inside. Transcoding is necessary in situations where you need to open the file in a program it doesn’t support or if you need to make changes to the file size, frame size or aspect ratio, frame rate or audio configuration. There are many programs to choose from. Most editors have something built in. They usually come with some templates for basic transcodes as a starting point. When playing around it’s good practice to find short segments where there is the most amount of motion and color. Set an in and out point around this section and export your tests using different bit rate settings. Once you find the right balance of file size verses quality, go ahead and output the whole job with that setting and cross your fingers. Here are a few free transcoding programs for you…

MPEG Streamclip

Handbrake

FFmpeg the easy (but limited) way FFmpegX, or full install on Mac with Homebrew. Download binaries and GUI at iFFmpeg.

I’m all out of time for now. Next week I will talk about what happened to your test files when you transcoded them.

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