Advanced Video Codec High Definition
Advanced Video Codec High Definition ( German advanced video codec high resolution ), AVCHD for short , is a digital format for video data. It was developed primarily for video recording with consumer - and prosumer - camcorders with recording on digital data carriers (e.g. SD card , flash memory , hard disk ). It uses the H.264 / MPEG-4 AVC codec and is in direct competition with the MiniDV formats and especially HDV , which uses the older MPEG-2 .
Origin and Distribution
The Advanced Video Codec High Definition standard was jointly developed by Matsushita ( Panasonic ) and Sony and presented on May 11, 2006. The two companies also hold the rights to AVCHD as a trademark.
On July 13, 2006, the start of licensing was announced. The format is currently also supported by Canon . Support from products from Pioneer , Samsung and Sharp has been announced. The licenses are issued for recording and playback devices as well as for software.
AVCHD Lite
The AVCHD Lite standard, presented on January 27, 2009, corresponds in all specifications to the AVCHD standard - with the only restriction that it is limited to the line format of 720 lines (720p) for video recordings and therefore does not support the 1080i line format for video recordings. AVCHD Lite is initially only intended for camcorders and digital cameras whose video recordings can be transferred to any playback or recording device that conforms to the AVCHD standard. The fact that from the standard corresponding to the AVCHD Lite recorded video data in the reproduction by a high scaling also video formats can be generated with a higher number of lines (see, for example, line doublers ), not available to the AVCHD standard against Lite.
This format requires less computing time for processing due to the lower resolution.
hardware
Sony, Panasonic and Canon launched the first AVCHD camcorders in 2006. Even Blu-ray poker players support this format usually because the Blu-ray Disc format was chosen for the internal data structure of AVCHD by Sony and Panasonic. If AVCHD clips are stored on DVD instead of Blu-ray media, they are called Mini Blu-ray or AVCHD discs . The data is stored on the discs in Universal Disk Format (UDF) version 2.5 or higher. This can lead to reading problems on PCs, as a corresponding UDF driver must first be installed before the discs can be read (currently applies to Windows XP and Linux ).
Products that can process AVCHD content can be advertised with a licensed logo (see illustration). The Sony PlayStation 3 ( firmware version 1.9 or higher) is able to play AVCHD videos from a memory stick or an external hard drive, whereby the size of the AVCHD files is limited to 4 GB due to the lack of support for the NTFS file system. The WD TV HD Media Player can also play AVCHD videos from an external USB hard drive and supports, among other things. a. the NTFS file system, which allows files larger than 4 GB to be processed. 4 GB is usually reached after approx. 40 minutes of recording time with HD recordings.
Commercial area
Meanwhile, both Panasonic and Sony have released camcorders that use the AVCHD format but are aimed at commercial users. It is to be expected that these will replace HDV camcorders in the medium term , as professional editing software can now also process AVCHD and the computing power of the computers used is sufficient for editing (see the section on video editing ). The companies market these camcorders under special brands.
AVCCAM
AVCCAM is the name of Panasonic Broadcast's line of professional video products that use the AVCHD format. This was previously listed as "AVCHD with professional features". Sometimes the HP@4.1 level of the AVCHD format is offered with a maximum bit rate of 24 Mbit / s, which corresponds to an increase compared to Panasonic's end-user models, which are limited to a maximum bit rate of 17 Mbit / s. Other manufacturers such as Canon, JVC, and Sony also offer 24 Mbps in their consumer camcorders.
NXCAM
NXCAM is the name of Sony's line of professional video products that use the AVCHD format (announced November 2009). NXCAM supports the 1080i, 1080p and 720p recording modes of AVCHD with data rates up to 24 Mbit / s. Sound can be recorded as uncompressed PCM audio recording. In contrast to AVCCAM, NXCAM does not support the usual film frame rate of 24p for 720p mode.
software
The format is now supported by most manufacturers of video editing software .
Details of the specification
The Advanced Video Codec High Definition is based on the MPEG-4 standard AVC / H.264 (MPEG – 4 Part 10). The first definition of this format is called AVCHD Format Version 1.0 .
Storage format
The compressed video and audio content is saved in an MPEG-2 transport stream (the usual file extension is .mtsfor MPEG transport stream ). The data packaged as a transport stream thus still has a kind of container that makes it easier to read the binary data even if either file or transmission errors have occurred or B. can not be started with a defined GOP reading, for example, if TS data is received from a television station, but you do not switch to the channel / transport stream exactly at the beginning of the GOP.
Video
In addition to the established television standards with 480 lines (see NTSC ) and 576 lines (see PAL or SECAM ) in the aspect ratios 4: 3 and 16: 9, the modes 720p / (30/25/24), 1080i / (60/50 ) and 1080p / 24 in 16: 9 aspect ratio. MPEG-4 AVC / H.264 is used as the compression method for the video signals .
In the specifications of the providers mentioned above, there is also the image resolution 1440 × 1080 for the 16: 9 format, but this does not conform to the H.264 standard, as this only provides square pixels for HD display in 16: 9 .
The video signals are recorded in the MPEG-4 data compression standard in order to then transfer them into an MPEG-2 transport data stream . Playback takes place at a data rate of, for example, 6, 9, 13, 18 or 24 megabit / s (plus sound and metadata ).
AVCHD uses a scalable compression method (MPEG-4) with different processing depths and provides an internal picture structure with a group of pictures of up to 15 pictures (frames). The color sampling is done in AVCHD with 8 bit, 4: 2: 0.
Audio
The compressed Dolby Digital (AC-3) recording process with a bit rate of 64 to 640 kbps and for 1 to 5.1 channels is available for audio signals . Alternatively, the linear PCM method can be used with a constant bit rate of 1.5 Mbps for 2 channels, but also variably with 1 to 7.1 channels. Sony's PlayStation 3 also supports DTS on AVCHD .
Data rate
The entire standard is defined up to a bandwidth (Level 5.1 / H444 profile) of 960 megabits per second and an image resolution of up to four million pixels. The usual data rates to be used at the end of 2008 were between 5 and 24 megabits per second, depending on the image resolution and compression rate . This corresponds to a recording time of around 5 (at 24 megabits per second) to 26 minutes (at 5 megabits per second) per gigabyte. For the use of the currently highest quality level of 24 megabits per second, Class 6 media are recommended that allow a gross data rate of 48 megabits per second.
Specification limit
At the beginning of 2010, Panasonic initially offered a camcorder whose maximum data rate for progressive Full HD recordings with up to 60 frames per second and, following the requirements of the high data volumes, can be set at 28 megabits per second above and thus outside the AVCHD specification.
In January 2011, Sony also presented a corresponding device with the option of setting up to 28 megabits per second.
If the data rate is outside the specification of AVCHD, you may experience difficulties when playing back with other devices.
AVCHD 2.0
At the beginning of July 2011 the extended standard AVCHD 2.0 was published. New specifications have been added to the AVCHD format for three-dimensional and high-definition recording in progressive mode up to 1080 / 60p. At the same time, the AVCHD 3D , AVCHD Progressive and AVCHD 3D / Progressive trademarks were introduced.
background
AVCHD was created by the Moving Picture Experts Group and converted into products by Sony and Panasonic , as they no longer wanted to rely exclusively on storage media with drives , such as tape drives , hard drives or DVD drives .
Comparison with tape recording
The magnetic tape offered the possibility of storing large amounts of data on a comparatively cheap data carrier . About 13 gigabytes can be stored on a mini DV tape. By using modern storage media, however, not only sequential , but also random access to the data is possible. This means the elimination of time-consuming winding and direct access to individual scenes, which are usually saved as individual files.
Memory cards were available for up to 16 gigabytes in May 2008, but were much more expensive than magnetic tapes . Since AVCHD achieves a significantly higher storage efficiency with an identical data rate compared to MPEG-2 (HD resolution) , the additional costs are put into perspective. H. the cost per time approached.
In addition, in the field of consumer video technology, the recording of FullHD content (1920 × 1080 pixels without interpolation ) was introduced for the first time at the same time as AVCHD , even though most of the camcorders on the market in 2008 still only achieve this resolution through interpolation. This also favored the better (than MPEG-2) compressing AVCHD format. At the turn of the year 2009/2010 the market had developed significantly: More and more recording chips were used that supported the FullHD format. In addition, the prices for camcorders and video-compatible digital cameras (mostly AVCHD lite for the use of SD (HC) cards) have fallen dramatically.
In November 2010, 16 GB SDHC memory cards were available for as little as 20 euros, but cards with a much higher capacity were also available.
Video editing
The AVCHD format is optimized for low data rates, not for simple editing of the film. Since video editing is increasingly in demand in the consumer sector, more and more consumer software editing solutions are being offered. The average processing in the Advanced Video Codec High Definition offer themselves some problems described in the following.
Computing effort
The high complexity of the compression algorithms requires a lot of computing time. A powerful computer with a 3 GHz dual-core processor and 2 GB of RAM could not avoid high rendering times (at the specification of AVCHD 2006) . The computational effort is heavily dependent on the use of the coding options and how well the rate-distortion optimization is set. AVC encoders with good performance are about eight to ten times the complexity of an MPEG2 encoder and decoding is about three times more complex than with MPEG-2 . The real-time limit (30 frames) for a two-core processor is 10 Mbit / s when using the CABAC codec, and 15 Mbit / s with a four-core processor. Without CABAC, both systems are above 20 Mbit / s.
Smart rendering
Only the transitions of the source clips are recalculated and the sections that have already been calculated are otherwise retained.
GPU support
Due to the large amount of data and the complexity of the calculations, manufacturers are increasingly using the computing power of the GPU using CUDA, ATI stream, or (rarely) OpenCL (often around a quarter to half of the real time).
Proxy cut
Some programs also offer the so-called proxy cut , whereby instead of the AVCHD data, low-resolution replacement clips are used (preview), and the actual calculation of the high-resolution AVCHD data is carried out in the background or after editing has ended.
Working format
Some editing software converts AVCHD to a simpler format before editing. The calculated result is then transcoded back into the target format (AVCHD).
Special hardware
At the beginning of 2011, processors of the Sandy Bridge 2 generation appeared on the market, which support encoding and decoding operations via the H.264 codec (which is the basis of AVC and AVCHD) directly in the processor. This results in some dramatic speed advantages, which in part outweigh the advantages of GPU-based processing in various editing programs. The Intel Core I7 Q2830 QM processor encodes AVCHD material almost as quickly as CUDA on a mid-range graphics card (status?).
Reduction in resolution
For private use, it can even be recommended to reduce the resolution from Full HD with 1920 × 1080 pixels to HD resolution with 1280 × 720 pixels during this process, because this hardly reduces the quality for the later viewer and the computing effort but greatly reduced. Nevertheless, this reduction in resolution - whether visible or not - leads to a measurable loss of quality.
3D generally increases the computational effort.
Big files
The recording on SD and SDHC cards, as well as on many built-in media, was made almost exclusively in the FAT32 or FAT file system. There is a maximum file size of 4 GiB, which is also standard for most AVCHD media such as Blu-ray discs . The recording of long scenes may produce more than one file, at the latest as soon as this file size is exceeded. Many editing programs cannot cope with this. However, camera manufacturers usually include software that can combine several recording segments into one large file (> 4 GiB), which can then be further processed with common editing software ( e.g. Sony PMB ). In addition, the exFAT file system for SDHC cards was introduced in 2006 , which also solves this problem.
See also
literature
- Wolfgang Wunderlich: Digital television HDTV, HDV, AVCHD for beginners and those switching to ISBN 978-3-00-023484-2
Web links
- AVCHD information web site (English)
- Panasonic press release
- Press release from Sony (English)
Individual evidence
- ^ AVCHD Information Web Site
- ↑ JVC recommendation: Class 6 required for 24Mb / s recordings ( Memento from August 3, 2012 in the web archive archive.today )
- ↑ Panasonic HDC-TM700 ( Memento from October 10, 2010 in the Internet Archive ) (PDF; 1.2 MB) data sheet
- ↑ CES 2011: Sony presents the new stars in the consumer electronics sky ( Memento from January 12, 2011 in the Internet Archive ) SONY HDR-CX700VE
- ↑ AVCHD Information Website - 1st July 2011 www.avchd-info.org (online)