問76
頻出度★☆☆
ストリーミングを利用した動画配信の特徴に関する記述のうち，適切なものはどれか。
平成27年度 春期 ITパスポート試験 問76
テクノロジ系情報メディア › マルチメディア技術
This question's explanation and your answers so far.
解説
問 76
Incorrectア
Incorrect. Streaming covers not only on-demand delivery, where finished data is placed on the server before it is delivered, but also live delivery (live streaming), where footage being filmed is encoded and sent out on the spot. Sports and event broadcasts are actually delivered this way, so the restriction that the data must be stored in advance does not hold.
Incorrectイ
Incorrect. Streaming gives priority to keeping up with the playback timing, so even when the communication quality degrades and packets are lost, playback often continues without waiting for retransmission, which leads to block noise, lower resolution, or dropped frames. Buffering and error correction can reduce the impact, but the degradation of image quality cannot be completely eliminated.
Incorrectウ
Incorrect. To keep playback from breaking up, the player must accumulate a certain amount of data in the buffer before playback starts. Because of this initial buffering, some preparation time (waiting time) always occurs, so saying that no preparation time is needed and that viewing can begin instantly is wrong. The correct understanding is that the wait is far shorter than with download delivery.
- エ
正解 The correct answer is エ. Streaming is a delivery method in which video or audio data is received over the network and the parts that have already arrived are played back one after another. The player first stores a few seconds of data in a buffer (temporary storage), and from then on it receives and plays back at the same time, so there is no need to wait for the whole file to finish downloading. The statement “Without waiting for all of the video data to be downloaded, playback starts at the stage when a portion has been loaded” therefore describes the very essence of streaming. By contrast, a method in which playback begins only after all the data has been downloaded to the device is called download delivery; the longer the video, the longer the wait, which is the usual point of contrast with streaming.
ここがポイント
- Streaming is a delivery method that plays data back in order while receiving it. Being able to start playback without waiting for all the data to be downloaded is the decisive difference from download delivery.
- Buffering, which temporarily stores data, is performed to prevent playback from breaking up, so the initial waiting time never becomes zero. In addition, streaming can support both on-demand delivery and live delivery.
用語