To comply with Level 4. In the early days of delivering video to mobile devices, levels mattered. Today, though, most current devices can play any level that you can deliver to it. Where levels remain important are requirements from service providers like Wowza. For example, figure 2 is from Encoding best practices for Wowza Streaming Cloud.
Unlike Profiles, which typically have a configuration option in the encoder, you comply with level settings by configuring your video within the constraints of that level. You see this in the encoding preset from Wirecast shown in figure 3.
While there is a specific configuration option for profile set to high , there is no option for level. Instead, you have to set the resolution, frame rate, and data rate parameters within the restrictions set by the level. Since the parameters are p30 , the preset conforms to level 4.
The final H. Presets change the configuration of certain codec options to allow streaming producers to choose their desired tradeoff between encoding quality and complexity.
For VOD video, for example, you might choose a high-quality preset that lengthens encoding time but optimizes quality. For live video, you may have to sacrifice quality to achieve real-time encoding, and choose a lower-quality preset.
While profile and levels are the same for all H. For example, figure 3 shows encoding with the x codec, which uses presets that range from Ultrafast to Placebo. Other H. Now that you know the basics, you should be able to configure your streams for optimum quality and compatibility. Although H. The three most commonly applied profiles are Baseline, Main, and High. Each of these profiles defines the specific encoding techniques and algorithms used to compress files. This is the simplest profile used mostly for low-power, low cost devices, including some videoconferencing and mobile applications.
Baseline profiles can achieve a compression ratio of about — i. They uses chrominance sampling, which means that color information is sampled at half the vertical and half the horizontal resolution of the black and white information. It can work with either progressive or interlaced video. It lacks some of the error resilience techniques supported by the baseline and extended profiles. This profile is mainly used for digital non-HD television broadcast. The high profile is a superset of the main profile.
The high profile offers a higher compression ratio than the others, at a slightly increased implementation complexity and computation cost. It is mainly used for high definition applications. The High 10 Profile Hi10P is built on top of the high profile, adding support for up to 10 bits per sample of decoded picture precision. The High Profile HiP adds support for the chroma subsampling format while using up to 10 bits per sample of decoded picture precision.
This profile builds on top of the high 10 profile. It supports up to chroma sampling, up to 14 bits per sample, efficient lossless region coding, and the coding of each picture as three separate color planes. Levels specify the size of the video a decoder must be able to handle. They specify a maximum bit-rate for the video and a maximum number of macroblocks per second.
On the left are products sold or otherwise distributed with AVC encoders or decoders installed, while on the right are various content categories that include video encoded into H. For content categories on the right, there are royalties for subscription services, that scale with the number of subscribers, but only start after exceeding , subscribers. There are also charges for Title-by-Title content sold to viewers pay-per-view , but only for content longer than 12 minutes in duration.
Continuing clockwise on the right, there is no royalty for H. Interestingly, the H. Initially, there was no royalty until at least January 1, , a policy that dissuaded many high-volume potential users from adopting H. Whatever the reason, those distributing free Internet video encoded via H.
In the streaming market, H. In , Adobe incorporated H. In terms of browser support, H. However, on January 11, , Google announced that they will remove H. However, Microsoft has released multiple plug-ins that enable H. With version On the content side, both YouTube and Vimeo quite loudly started supporting H. Virtually all videos produced for iTunes are also encoded in H. In terms of video quality, H.
Regarding WebM, there is some disagreement. Codec selection is one of the most fundamental decisions facing streaming media producers. In order to make the right decision, producers should know the characteristics and costs of any technology that they choose.
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