Peak bit rate-based VBR tab

The following settings are applicable to a profile that uses peak bit rate-based VBR encoding.

• Audio format. Click a setting for the audio content. The setting determines the target audio bit rate, sampling rate, and also whether the audio is intended for playback on mono or stereo speakers. A higher sampling rate yields higher-quality audio but requires more bandwidth or results in a larger file. Ideally, you want to achieve the right balance between bit rate and sampling rate.
• Audio peak bit rate. Type the peak bit rate that you want to use for the audio content. While encoding, the encoder determines the audio quality that can be achieved without exceeding the peak bit rate.
• Audio peak buffer size. Type the maximum buffer size (in seconds) that the client should wait before playing the content that was encoded at the peak audio bit rate. If you are encoding for playback on a hardware device, type the buffer size, in seconds, corresponding to the buffer size on that device. The default peak buffer size is 3 seconds. For best results, this number should always be equal to or lower than the buffer size (if you are using CBR encoding for the video) or peak buffer size for video (if you are using peak bit rate-based encoding for the video).
• Video size. Type the size (in pixels) you want to use for the encoded video. Use numbers from 16 through 2000. The frame size of the encoded video will be resized to match the size you specify. Select the Same as video input check box to match the frame size of the source video.
• Frame rate. Type the number of frames per second (fps) for the video stream. The amount that you adjust this value to depends on the speed of your computer processor and whether you are encoding high-motion or low-motion video. High-motion video generally looks smoother if you use a higher frame rate, but a higher frame rate increases the amount of work the processor must perform. The setting you specify represents the maximum fps; the actual fps might be lower.
• Key frame interval. Type the number of seconds that you want to separate key frames. All frames between key frames are delta frames, which are considerably smaller than key frames but have poor visual quality. If you increase the time between key frames, the size of the video (in bytes) gets smaller because fewer key frames are used. If you decrease the time between key frames, the size of the video increases. Increase the key frame interval for content with a static background, such as cartoons. Decrease the key frame interval for high-motion content, such as a sporting event.
• Video bit rate (average). Type the average bit rate (in bits per second) you want to use for the video portion of your content. Type K for kilobits, M for megabits, or G for gigabits. At any point, the bit rate may exceed the average bit rate but the overall bit rate will not exceed the average bit rate.
• Video peak bit rate. Type the peak bit rate (in bits per second) that you want to use for the video content. While encoding, the encoder determines the image quality that can be achieved without exceeding the peak bit rate. If you are encoding for playback on a hardware device, such as a DVD player, type the reading speed of the hardware device.
• Video peak buffer size. Type the maximum buffer size (in seconds) that the client should wait before playing the content that was encoded at the peak video bit rate. If you are encoding for playback on a hardware device, type the buffer size, in seconds, corresponding to the buffer size on that device. The default peak buffer size is 5 seconds.
• Decoder complexity. If you are targeting a hardware device other than a computer, you can specify a category of complexity for the content being encoded. Some hardware devices only support certain categories. (Refer to the documentation for your device for more information.) Note that the Complex option is intended for playback on computers. Typically, you should select Auto, which enables the correct complexity setting to be selected automatically during encoding.
• Script bit rate. Type the bit rate (in bits per second) that you want to use for scripts. The value must be between 1,000 bps and 10,000 bps. Type K for kilobits.