1. Field of the Invention
The present invention relates to a recording device for recording a digital broadcast onto a random-access recording medium such as an HDD or a DVD in compressed form, a recording method used by the recording device, and a computer-readable program that realizes the functions of the recording device. The invention in particular relates to improvements in recording digital broadcast data in response to a user's manual operation.
2. Description of the Related Art
In recent years, television broadcasting has undergone a transition from analog signals to digital signals. This ongoing transition indicates that models which provide support for digital broadcasting will become the dominant form of recording devices. In digital broadcasting, video of a television program is transmitted via a channel in compressed form. Such compressed video takes the form of transport stream (TS) packets. Digital broadcast-ready recording devices record the video onto a recording medium in this TS packet form. Since there is no quantization loss associated with encoding/decoding operations, the recording devices can record the video with high picture quality.
Meanwhile, playback of a television program which is broadcast by digital broadcasting differs from playback of a television program which is broadcast by analog broadcasting on the following point. In digital broadcasting, there is a substantial time interval between reception and playback. That is to say, a video frame which is being played back is a video frame that was received earlier than a video frame which is being received.
This time interval is caused by a buffering delay. In digital broadcast playback systems, TS packets equivalent to a time period of about one second need be accumulated in a buffer to obtain frame data which is to be decoded. This causes a buffering delay, which results in a time interval between reception and playback. This time interval between reception and playback poses a problem when the user performs manual recording. Manual recording refers to an operation of recording data which is triggered by the user's record request. The user performs manual recording while viewing playback of a video frame. The user's intension here is to record the currently-played video frame onward. However, the currently-played video frame was received well before the currently-received video frame due to the above time interval between reception and playback, so that the recording device cannot immediately obtain the currently-played video frame. This being so, the recording device begins recording from the currently-received video frame onward. This causes first several video frames to be missing in the recording. Though the number of missing video frames is not high, this is a serious detriment to the performance of digital broadcast-ready models as compared with analog broadcast-ready models. In analog broadcasting, a video frame which is being played is approximately the same as a video frame which is being received. Therefore, a loss of first several images does not occur when manual recording is performed. A failure of digital broadcast-ready models, which are supposed to be the latest in broadcast recording technology, to achieve the same function as analog broadcast-ready models may lower their popularity on the ground that the performance of digital broadcast-ready models is poorer than that of their analog counterparts. This seriously affects manufacturers' marketing strategies in expectation of replacement demand for digital broadcast-ready models.