探测器函数然后保存帧并注销自身的注册。

The probe function then saves a frame and deregisters itself.

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探测器又叫做缓冲区探测器—它只在实际的数据块上被调用，比如视频帧。

The probe is what's called a buffer probe-it gets called only on actual blocks of data such as frames of video.

youdao

如果探测器函数返回TRUE，该帧被传递给流，如果返回FALSE，该帧将被丢弃。

If the probe function returns TRUE, the frame is passed down the stream, but if it returns FALSE, the frame is dropped.

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