A 6 Mhz Channel can accommodate 17.89 Megabits per second worth of data. With the advent of digital television, broadcasters and cable companies are capable of tuning the resolution, bitrate, and packaging of their channels. This means that a multiple core system cannot be used to fullest effect, and that playback must instead rely on the raw clock speed of a single core.Ĭentral to any discussion of digital reception is the notion of multiplexes. The larger problem for linux playback is the failure to encode in so-called "slices," which render linux systems (currently) incapable of multithreading the playback. In reality, the quality retained by processor intensive encoding options is relatively small. This is generally due to inexperienced transcoders using options that purport to retain higher quality at lower bitrate, as well as neglecting to utilize sliced encoding.
In some cases, a lower bitrate file may actually be more difficult to play. In effect, processor requirements for the "real thing" may be up to four times as high as the user expects. While "true" Blu-ray and HD-DVD material may be encoded up to 40 Megabits per second, television is broadcast in bitrates up to 17.89 Megabits per second, and many "1080p rips" found on the internet are transcoded below 10 Megabits per second. In reality, a full-bitrate H.264 or MPEG-2 from a Blu-ray/HD-DVD Disk may be substantially more difficult or impossible to play back for the same machine. At proportionately lower bitrates, processor requirements are also proportionately lower. Most pirated HD material has been transcoded to substantially lower bitrates, often cutting the file size/bitrate more than in half.
#HDTV VIDEO CAPTURE CARDS 1080P#
Users who get their 1080p material via bittorrent or other questionable means often think that because they are able to play back the file, their system is capable of playing back all 1080p material. Uninformed users frequently make a point of asking whether their hardware is capable of "1080p playback." Similarly uninformed users reply that a given setup is "enough" or "not enough." In reality, resolution of the material is a relatively minor part of the playback equation. Playing 1080p H.264 can often be nightmarish for those unfamiliar with tweaking playback options.īitrate (Or, if you read nothing else, read this)
#HDTV VIDEO CAPTURE CARDS 720P#
Playing 720p and 1080i H.264 streams (at full bitrate) can be difficult, even on recent systems. This comes at a much higher computational expense. Accordingly, a full-channel-bitrate (17.89 Megabit/s) H.264 stream compared with an identical-bitrate MPEG-2 stream will look substantially better. H.264 can achieve identical quality to MPEG-2 at 60% of the bitrate. H.264 is a newer standard, but improves upon MPEG-2 in several ways. Playback is not computationally demanding, and most modern dual-core (and many recent single core) systems can easily manage playback. MPEG-2 is a well understood, established video format. In the United States, ATSC permits only MPEG-2 as the codec. When agreeing upon standards for digital television, Europe and much of the rest of the world implemented the DVB standard, which permits broadcasters to use either MPEG-2 or H.264 codecs. The modulation for each is different, sometimes requiring different hardware. HDTV can be delivered via three mediums: Broadcast (Over the Air), Cable, and Satellite. In Europe, Australia, and other parts of the world using the DVB standard, some streams are available as MPEG-2, and others as h.264. In North America, HD material is transmitted in MPEG-2 format. HD material is received as a digital stream and written directly to disk.
Unlike analog television capture, where a hardware encoder is desirable, compression of High Definition material takes place at the provider. A digital tuner works much like a modem extracting the original digital data. HDTV (High Definition Television) is sent as stream of binary data encoded in the radio spectrum.
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