1. Field of the Invention
The invention relates to non-linear editing systems and, more particularly, to a media editor for the storage, editing and retrieval of audio/visual information.
2. Description of the Related Technology
Linear video editing systems, such as those for videotape and photographic film, are old in the art. In contrast, current personal computer (PC) systems, such as those of the Apple.RTM. Macintosh.RTM. and Intel.RTM. architecture, offer non-linear video editing systems. Non-linear editing on computer oriented systems involves digitizing analog media data recorded from a linear source, such as videotape or film, and storing the digitized media data on a storage device, such as a magnetic disk drive. Once digitized, the non-linear editing system permits rapid access to media data at any point in the linear sequence for subsequent manipulation of media data portions into any order. For example, non-linear editing systems enable the combination of audio clips with other video clips and the formation of new clips using portions of other clips.
The non-linear video editing capability typically resides in a plug-in card for the NuBus or PCI expansion bus of a Macintosh architecture PC or the ISA, EISA or PCI expansion bus of an Intel architecture PC. These non-linear video editing systems typically use compression techniques developed by the Joint Photographic Experts Group (JPEG) or the Motion Picture Experts Group (MPEG). For example, in U.S. Pat. No. 5,577,190, Peters discloses a media editing system that receives, digitizes, stores and edits audio and video source material, using JPEG compression, for later manipulation by a computer, such as an Apple Macintosh. Similarly, in U.S. Pat. No. 5,508,940, Rossmere, et al., disclose a multimedia random access audio/video editing system including a main control unit that receives data and commands over a SCSI bus from a personal computer having an analog I/O board coupled to audio and video processing boards using JPEG compression. Moreover, Reber et al. disclose a system and method for the management of media data in a non-linear editing system that enables dynamic linking of digitized media data with a specific source reference at run time in U.S. Pat. No. 5,584,006. Lastly, in U.S. Pat. No. 5,438,423, Lynch, et al., disclose a system and method for continuously storing the video content of a program, using JPEG or MPEG compression, in a recirculating random access buffer having sufficient capacity to store a substantial portion of the program.
Unfortunately, consumers currently have no cost effective alternatives for enhancement of their camcorder movies and digital pictures without having to incur substantial costs to purchase a personal computer with a high resolution computer graphics monitor, associated add-in cards and software for non-linear editing. In addition, conventional non-linear editing systems are designed for expert users, such as a professional movie editor, to edit a large number of unrelated movie clips stored on the same linear film or videotape. Thus, conventional non-linear editing system tools are complex and require a high degree of manual interaction and configuration to produce a final edited result. In contrast, consumers often capture closely related events, such as vacations and birthday parties, on videotape using their camcorders. To edit these camcorder tapes, consumers require easy to use non-linear editing systems that facilitate editing without a high degree of computer or editing skill and time spent to configure plug-in cards and software. Similarly, manufacturers currently have no viable, cost effective means for incorporating non-linear editing functionality into their home entertainment components because currently available non-linear editing systems are specifically adapted for personal computer plug-in applications and functionality, instead of home entertainment components. Conventional non-linear editing systems, such as Adobe.RTM. Premiere.RTM., provide user interfaces designed for rendering on high resolution non-interlaced computer graphics monitors. Although computer graphics monitors are viewed from a distance of one to two feet, consumers must often zoom-in on portions of the user interface to perform non-linear editing functions. In contrast, conventional television sets having low resolution interlaced displays, commonly available in home entertainment environments, render poor quality images of these user interfaces designed for high resolution graphics monitors. To compound matters, consumers often view their television sets from a distance of several feet, where a poor quality rendition of a user interface severely impedes its use. Consumers require a non-linear editing system adapted for use with conventional television sets.
Furthermore, current personal computer based non-linear editing systems are specifically adapted to an RGB (red, green and blue) color space used for non-interlaced computer graphics monitors or CRTs. However, RGB is a poor choice for representing real-world images because equal bandwidths are needed to describe each color component while the human eye is more sensitive to luminance (the Y or black and white component) than color components (the U and V components). The equal bandwidth of the RGB format provides the same pixel depth and display resolution for each of the three color components. For example, an NTSC video frame requires about 1012 kilobytes of RGB data, whereas only 675 kilobytes of YUV (4:2:2) data are needed for the same NTSC video frame. Television displays are adapted to receive 29.97 NTSC frames/sec. Thus, to receive an uncompressed NTSC video feed, a non-linear editing system requires a bandwidth of at least 30.3 megabytes/sec. To support the increased bandwidth requirements of the RGB format, non-linear editing systems require expensive dual port video RAMs, instead of low cost synchronous DRAMs. A reduction in the RGB bandwidth requirements needed for PC based nonlinear editing systems is needed to make a non-linear editing system affordable for home use.
In addition, some conventional PC systems use a block memory mover, such as the blitter of the Commodore AMIGA, to manipulate the pixels comprising a rectangular region of a computer display image without intervention of the microprocessor. A personal computer can display images on its display in a wide variety of resolutions, such as 640.times.480 pixels or 1280.times.1024 pixels. A plurality of RGB bits represents each pixel of a display image. Typically, the block memory mover has to copy the bits comprising the pixels of the rectangular region from one location of frame buffer memory to another location of frame buffer memory, implemented using expensive video RAM, to maintain standard computer display resolutions. Unfortunately, conventional block memory movers are designed only to move pixels within a controllable mask, which merely defines whether or not to move specific pixels of the displayed image. Thus, PC based non-linear editing systems do not use conventional block memory movers to perform non-linear editing functions, such as shaped cuts and mixing. Moreover, the use of a block memory mover to perform shaped cuts degrades the output video quality as the fine edges of a shaped cut appear very jagged without some form of anti-aliasing when displayed on a low resolution television set. To bring non-linear editing systems into the home, improved block memory movers capable of performing non-linear editing functions are needed.
Lastly, current PC based non-linear editing systems use conventional memory controllers to access frame buffer memory, which is implemented using expensive FIFOs or VRAMs in order to meet the bandwidth requirements for video data transfers. However, for the same storage capacity, a FIFO currently costs about 20 times more than a DRAM, while a VRAM currently costs about 5 times more than a DRAM. Unfortunately, conventional memory controllers can not support the bandwidth requirements for video data transfers by accessing DRAM memory. Thus, to provide cost effective, non-linear editing systems for home use, consumers require an improved memory controller capable of supporting video bandwidth requirements using DRAM memory. Moreover, conventional non-linear editing systems also increase system cost by using additional dedicated processors, such as audio DSPs or the CPU of the personal computer, for audio editing functions. In summary, consumers have a substantial unmet need for cost effective, non-linear editing systems for home audio and video applications that do not require the use or purchase of an expensive personal computer.