Patent Application
20090300242
The present disclosure relates to the subject matters contained in Japanese Patent Application No. 2008-143506 filed on May 30, 2008, which are incorporated herein by reference in its entirety.
The present invention relates to an audio data processor and a method for processing audio data of main audio and sub audio for external output, for example, in an optical disc player.
Large-capacity optical discs such as DVDs have come into remarkably wide use recently. Most of the existing DVD players are compliant with a digital audio output based on a transfer method such as High-definition Multimedia Interface (HDMI). There is a prospect that DVD players only compliant with the HDMI-based audio output but provided with no analog audio output terminal will appear in the future.
The HDMI has a one-way bus for video and audio data. The one-way bus can transfer audio data as a compressed bit stream at a high speed. In HDMI version 1.3 or later, a transfer format of High-Bit-Rate Audio (HBR Audio) has been defined for bit stream transfer of high-bit-rate audio data such as TrueHD or DTS-HD.
Although a large-capacity optical disc has contents containing various kinds of audio data such as main audio and sub audio, the HDMI is not a specification that bit streams of the various kinds of audio data can be parallel-transferred to an external apparatus such as an AV amplifier. For this reason, when, for example, the one-way bus is occupied by audio data of main audio output as a bit stream, audio data of sub audio cannot be output and must be discarded.
To solve such a problem, there has been heretofore proposed a method in which audio data of main audio is output as digital data from HDMI, etc. whereas audio data of sub audio is converted from digital signal to analog signal and output as analog data from an analog audio output terminal. An example of such method is disclosed in JP-A-2007-213663.
It is however impossible to apply the method described in the publication JP-A-2007-213663 to the case where there is no analog audio output terminal provided.
A general configuration that implements the various feature of the invention will be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.
An audio playback system according to an embodiment of the invention will be described below with reference to the accompanying drawings.
The disc controller 11 reads a program stream from an optical disc DK and feeds the program stream to the demultiplexor 12. The demultiplexor 12 demultiplexes the program stream by packet types such as video and audio. With respect to each audio packet, audio data of main audio and audio data of sub audio are decoded by the decoder 13, mixed by the mixer 14 and output to a headphone terminal.
The audio data of main audio and the audio data of sub audio are further fed from the demultiplexor 12 to the main audio output controller 15 and the sub audio output controller 16 respectively. The main audio output controller 15 is configured to perform a process of converting the audio data of main audio obtained from the program stream into an IEC61937 format having an auxiliary recording space while embedding time information for specifying playback time in the auxiliary recording space. The sub audio output controller 16 is configured to perform a process of selecting part of the audio data of sub audio obtained from the program stream in accordance with the time information of the output request.
The AV amplifier 20 has an HDMI interface 21, a decoder 22, a mixer 23, and a time stamp analyzer 24. The HDMI interface 21 is a digital interface which receives audio data of main audio through the one-way bus B1 and receives audio data of sub audio through the two-way bus B2. The audio data of main audio and the audio data of sub audio obtained from the HDMI interface 21 are decoded by the decoder 22, mixed by the mixer 23 and output to a speaker output terminal. A bit stream obtained by adding time information successively to the audio data of main audio is transferred from the HDMI interface 17 to the HDMI interface 21 through the one-way bus B1. The time stamp analyzer 24 analyzes the bit stream, acquires the time information successively from the bit stream and issues a sub audio request command to request a sub audio output for each piece of the time information. The sub audio request command is transferred from the HDMI interface 21 to the HDMI interface 17 through the two-way bus B2 and fed from the HDMI interface 17 to the sub audio output controller 16.
Upon reception of the bit stream of audio data of main audio, the HDMI interface 21 of the AV amplifier 20 feeds the bit stream both to the decoder 22 and to the time stamp analyzer 24. The time stamp analyzer 24 extracts time information from the stuffing areas of the IEC61937 format in the bit stream and analyzes the time information in step S4. Then, the time stamp analyzer 24 issues a sub audio request command to request a sub audio output. The sub audio request command, which contains time information attached thereto as a time stamp for specifying playback time of audio data of sub audio, is fed to the HDMI interface 21. Although description has been made on the case where the attached time information coincides with the time information extracted from audio data of main audio, the two pieces of time information need not coincide with each other. That is, when the audio data of main audio to be played back simultaneously with the audio data of sub audio requested to be output has been already received, the start of playback of the audio data of main audio need to be delayed until the audio data of sub audio is received. Therefore, if an offset value is added to the time information attached to the sub audio request command, the audio data of sub audio to be played back simultaneously with the audio data of main audio can be received prior to the audio data of main audio so that the aforementioned delay can be dispensed with.
The sub audio request command is fed from the time stamp analyzer 24 to the HDMI interface 21 and output to the two-way bus B2 in step S5. In the reproducing apparatus 10, the HDMI interface 17 receives the sub audio request command and feeds the sub audio request command to the sub audio output controller 16. The sub audio output controller 16 analyzes the sub audio request command in step S6 and selects part of the audio data of sub audio corresponding to playback time specified by the time information of the sub audio request command. The part of the audio data of sub audio is fed from the sub audio output controller 16 to the HDMI interface 17 and then output to the two-way bus B2 in step S7.
Upon reception of the audio data of sub audio, the HDMI interface 21 of the AV amplifier 20 feeds the audio data of sub audio to the decoder 22. The decoder 22 decodes the audio data of main audio received from the one-way bus B1 and the audio data of sub audio received from the two-way bus B2 in step S8 and feeds the decoded audio data to the mixer 23. In step S9, the mixer 23 mixes the audio data of main audio and the audio data of sub audio obtained as decoded results in the decoder 22 and outputs the mixed data to a speaker terminal.
In this embodiment, a bit stream obtained by adding time information for specifying playback time successively to audio data of main audio is output to the one-way bus B1, an output request issued for each piece of the time information obtained successively from the bit stream in the AV amplifier 20 is acquired from the two-way bus B2, and part of audio data of sub audio corresponding to the time information of the output request is output to the two-way bus B2. That is, when the two-way bus B2 is provided in addition to the one-way bus B1, the two-way bus B2 can be used for achieving a digital output of audio data of sub audio. Moreover, in the AV amplifier 20, simultaneity in playback time between audio data of main audio and audio data of sub audio can be achieved by the time information. Accordingly, audio data of sub audio can be output as digital data through the two-way bus B2 without spoiling of simultaneity in playback time with audio data of main audio output as digital data through the one-way bus B1.
In conventional audio compression techniques such as Dolby Digital (trademark registered) and DTS (trademark registered), for digital output (non-HBR Audio output) of audio data of main audio and audio data of sub/effect audio to an external apparatus, these audio data may be decoded by the decoder 13, mixed by the mixer 14 and then re-encoded. The re-encoding can be however dispensed with when the time stamp (time information) attaching method is used as described in this embodiment. Accordingly, a simpler system configuration can be achieved.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-143506 | May 2008 | JP | national |
