Cirrus Logic Inc.

Jeffrey G Ort

Daniel Thomas Daum

Mark A Rosenau

Tzoyao Chan

Chih-Ta Sung

Richard Chang

Daryl G Sartain

Yuanyuan Sun

A technique for providing PCI bus mastering compatibility for legacy PCI bus devices which may not support PCI bus mastering RETRY protocols. DLDMM provider software in a device driver for a target device may provide a callback signal at a callback address to DLDMM client software in a device driver for a bus mastering PCI device. The callback address may be used by the DLDMM client software to signal the bus mastering PCI device to suspend operation in the event of an interrupting event. The bus mastering PCI device may then generate in driver software a RETRY signal to the device driver of the target device. If the interrupting event is over, a signal may be sent by the DLDMM provider software in response to the RETRY signal to the DLDMM client software indicating that the bus mastering device may resume operation. The bus mastering device may then resume operation where left off. The technique of the present invention has particular application to multimedia computer systems where a bus mastering device (e.g., MPEG decoder or the like) may wish to stream MotionVideo.TM. data to a target adapter (e.g., VGA controller or the like) using bus mastering techniques. Prior art PCI VGA adapters may not support PCI RETRY protocols and thus attempts to send data to such devices using bus mastering may fail.

PCI bus master retry fixup

A method and apparatus for handling both proprietary and non-proprietary formatted compact discs in the same video playback system. In one embodiment, the audio and video data signals are in a Moving Pictures Expert Group (MPEG) format. Portions of the novel system operate within a high level format independent software library and portions of the novel system operate within a low level software driver of the playback system that receives disc information from a proprietary or non-proprietary disc present to the playback system to be played. The novel system of the present invention includes a disc format determinator for checking the data contained on a disc to see if it includes proprietary information specific to the playback system. In the present invention the proprietary information may be either VideoCD or CD-I disc format information. If a disc presented to the playback system is formatted for a non-proprietary disc format i.e., VideoCD or CD-I, the disc format determination procedure configures the disc in order to enable the playback system to read and playback information contained on such a disc.

Method and apparatus for handling proprietary and non-proprietary

A multimedia system including an audio/video decoder/decompresser for decoding/decompressing a compressed encoded audio/video data stream to generate video images for display and audio signals for audible reproduction. The multimedia system includes an integrated system and video decoder with an audio/video synchronization circuit for substantially synchronizing the display of video images with audio playback. In addition, a step control is provided to allow for viewing of video images on a frame-by frame basis or to freeze or play video in slow motion. When step control is activated, audio output is muted. Audio data corresponding to displayed video is transmitted to the muted audio decoder. An internal system clock may be suppressed to the system clock counter. An external CPU may provide system clock start times corresponding to video frames to be displayed. The external CPU may increment the system clock counter by a an amount corresponding to the difference between a successive frame or number of frames. When nominal playback is resumes, the audio and video data streams are substantially in synchronization.

Stream synchronization method and apparatus for MPEG playback system

A system and method for handling errors encountered in an audio/video data stream during playback. In one application, the audio/video data stream originates from an MPEG (e.g., Motion Pictures Expert Group) source and is a playback file of the MPEG format. Upon receiving an error interrupt originating from a hardware video processor unit, the novel system executes a group of predetermined error handling processes. A playback error can result from bad data within the playback file's data stream, the data bus, or other transmission error. One error recovery process used by the novel system causes the playback system to skip B and P frames until an I frame is reached which is processed normally and playback resumes. Another error recovery process causes the playback system to seek forward a predetermined number of seconds and/or frames to resume normal playback in order to avoid a bad media sector. A third error recovery process causes the playback system to seek forward to a next sequence header to resume normal playback. The processes are performed in a novel error sequence in which repeat errors are handled by different processes. Back-to-back errors occurring outside a predetermined time or data window are not considered repeat errors and reinitialize the error sequence. If the error sequence fails to avoid the error, the user or viewer is informed that the playback file may be non-MPEG compliant and playback is temporarily terminated.

System and method for error handling during playback of an audio/video

A method for causing a computer controlled digital playback system to seek to a requested location within a selected playback file recorded in variable data rate encoding format (e.g., MPEG). The playback file is stored in a suitable recording media. The novel method receives a seek command to a requested playback time referenced by a time unit (e.g., seconds) or a frame number and also accesses an upper rate bound from a system header. The rate bound indicates the maximum data rate of the encoded data in the playback file. Using the rate bound and the requested playback time, an approximate location is determined in the playback file and the playback file is seeked to that approximate location. The method reads a first available time stamp near the approximate location and checks if the discovered time stamp matches with the requested playback time within a predetermined degree. If not, the novel method computes an adjusted data rate based on the discovered time stamp and the approximate location. This adjusted data rate is averaged with the prior data rate to obtain a current data rate used to compute a new approximate location. The above is repeated until a match occurs or until the new approximate location equals the old approximate location. Upon a match, an I frame or a sequence header is located, initialization information is pre-pended, the video processor unit is flushed, and the playback file data is downloaded for playback beginning at the requested playback time.

Method for seeking to a requested location within variable data rate

A method and system for synchronizing audio and video data signals that are in a signal format wherein the audio and video data signals are not interleaved but originate from separate sources and arrive at a constant frame rate. In one embodiment, the audio and video data signals are in an Moving Pictures Expert Group (MPEG) format. Portions of the novel system operate within the hardware of a video processor unit and portions of the novel system operate within a software driver of a computer system that receives the audio and video data signals. Audio and video data signals are referenced by a presentation time stamp (e.g., VPTS for video and APTS for audio) encoded in the data. Using these stamps, the novel system (via the video processor unit) determines if the video signal is ahead or behind the audio signal by a small number of frames, x, and if so, the video processor unit either pauses or skips frames in its video display unit hardware to regain synchronization. If the video processor unit determines that the video signal is ahead or behind the audio signal by more than x frames, a software driver operating on the computer system is informed of the difference and the software driver instructs the video processor unit to skip or pause frames within its system parsing unit hardware using a host interrupt driven mechanism to regain synchronization. Using this method, the digital video signal is effectively synchronized to the reference digital audio signal.

System and method synchronizing audio and video digital data signals

A multimedia system including an audio/video decoder/decompresser for decoding/decompressing a compressed encoded audio/video data stream to generate video images for display and audio signals for audible reproduction. The multimedia system includes an integrated system and video decoder with an audio/video synchronization circuit for substantially synchronizing the display of video images with audio playback. An audio presentation time stamp (APTS) is detected in the compressed/coded audio data stream in the integrated system and video decoder and stored in a data latch. The compressed/coded audio data stream is fed to an audio decoder which decodes/decompresses the audio data and outputs and audio signal. The audio decoder detects when audio data corresponding to an APTS had been output and sets a corresponding flag. The flag indicates to the integrated system and video decoder that a corresponding audio segment had been decoded/decompressed and output. The integrated system and video decoder then synchronizes the video output with the audio output by repeating or skipping frames of video data.

Method and apparatus for audio and video synchronizing in MPEG playback

A multimedia system including an audio/video decoder/decompresser for decoding/decompressing a compressed encoded audio/video data stream to generate video images for display and audio signals for audible reproduction. The multimedia system includes an integrated system and video decoder with an audio/video synchronization circuit for substancially synchronizing the display of video images with audio playback. A method is described for detecting when the playback of audio and the display of video images are out of synchronization. The circuitry includes three programmable registers, a finite state machine and one full adder using an audio presentation time stamp and the video presentation time stamp. The method uses a rounded programmable bias value which is compared with the difference between the video presentation time stamp and the audio presentation time stamps. The difference may included the latency delay of the audio and video display devices to more properly reflect the synchronization status between audio and video. The circuit area used by the circuitry has been minimized by selective rounding or truncation of the audio presentation time stamp and the video presentation time stamp without sacrificing the accuracy or speed of determining the synchronization between audio and video.

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Kirkland, WA, United States of America

Jeffrey G Ort