What is Video Transcoding?
What are the types of file format used in Video Transcoding?
In this article, we focus on “file-based transcoding” – the process of taking one video file and converting it to create a second – but there are other types of transcoding, for example converting video streams.
Video formats can be broken down into 6 parts.
How video transcoding process is carried out?
The video transcoding process requires two main inputs. First, details of what the input file or format is and second, the full set of parameters for the output. Typically, the details of what the input file/format is are determined through performing an analysis of the media. The parameters for the output are typically determined by rules in the media supply chain system, or derived from metadata based variables in the workflow engine. From here, we create what is known as a pipe.
The pipe exists for all the persisting components in the media file – video, audio, ANC and metadata, splitting where needed between components. Through analysis of the file and instruction, the transcoder can configure the pipe at the start of the transcode, meaning that the processes involved can happen in a concatenated way, rather than sequentially, reducing the duration of the transcode process.
For simplicity, we’ll start with just one component, the video.
The first step is to demux the input. This means to extract the compressed video data from the packaging and/or wrapper.
The second step is to decode the video – decompressing it back to, or as close as possible, the uncompressed original frames.
During a video transcode process, there are a number of processes that can, or need to be applied to the video. These include things like scaling, if the size of the output is different from input, de-interlacing or interlacing, if we’re going from a progressive “P” picture to interlaced “I” or vice-versa, and in advanced transcoders may include more advanced image processing that changes elements of the picture to improve the perceived results of the video encode process.
Taking the video and encoding it with the required destination codec.
Packing the video into the wrapper and or packaging and, where needed, combining it with the other components.