![]() ![]() ![]() This is also known as MPEG-4 Advanced Video Coding (AVC) or H.264 it is the most used codec today. MPEG-4 Part 2 videos mostly come in an AVI container, but MP4 is also seen often. Some encoders that output MPEG-4 Part 2 video are DivX, its open sourced ripoff XviD, and Nero Digital. It doesn't work so well for HD or 4K content anymore. It offers good quality at practical file sizes, which meant that you could burn a whole movie of 90 minutes length onto a 600 MB CD (whereas with MPEG-2 you would have needed a DVD, see my answer here). This is probably the one that was used mostly to encode videos for the web in the mid-2000s, but it has been superseded in the meantime. DVB-T or satellite, and legacy applications where compatibility is important. MPEG-2 video is mostly used for DVDs and TV broadcasting, e.g. "I have a file in MPEG format" is very ambiguous". This adds to the confusion, but just know that "MPEG" alone doesn't mean anything, e.g. Note that "MPEG" can refer to both codecs and containers, as you will see below. those created by Google or the Alliance for Open Media, which are competitors to the MPEG standards. But there are some other, royalty-free codecs as well, e.g. Interestingly, almost all of them were created by the Motion Picture Experts Group (MPEG). These days, you will probably only find videos encoded with the codecs I will mention below. The bitstream is then multiplexed into a container. So, all in all, let's just say that an encoder will: Both encoders will deliver a standardized bitstream that can always be decoded by a H.264-compliant decoder. The mere fact that you can optimize encoding makes for a competition here. Both claim to deliver good quality, of course. Mainconcept is a very good commercial encoder, whereas x264 is a free and open source one. The standard's name is H.264 – that's not the name of the actual encoder. A case example – H.264īefore we mix up terminology, let's take an example. This is the reason why you will find so many encoders for the very same codec, and some of them even commercial. Often they supply a reference encoder and decoder, but how an encoder is then written to match such a format completely is up to manufacturers. For example, they will say: "The bitstream format has to be like this", "The 0x810429AAB here will be translated into that", etc. Nowadays, when a video codec is specified, the institutions that take part in it usually only specify the syntax of the standard. ![]() This happens to be valid for video, audio, but you could also think about cryptography (an encoder needs an appropriate decoder to display an encrypted message). What is a codec?Ī codec is short for encoder/decoder, which basically just means the following: Data generated by an encoder can always be decoded by an appropriate decoder. There are often multiple encoders for one particular codec.Īs you can see, we'll have to explain a few things here. A particular encoder (e.g., x264, libvpx) is responsible for turning an input stream into a codec-compliant bitstream.A container (e.g., MP4, MKV) is responsible for keeping them together and this is also what you usually open up in your media player of choice.A codec (e.g., H.264, HEVC, VP9) is only responsible for the video or audio part, and one or more codecs can be merged into a container. ![]()
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