Adobe 65009626 User Guide - Page 87

USING SOUNDBOOTH CS4 83 Saving audio and video files Undershoot [% target] Available only when exporting in the FLV video format using the On2VP6 codec, this option lets you specify the percentage of the target data rate to shoot for so that additional data is available in the buffer to improve difficult sections. Quality Available only when exporting in the FLV format, this option lets you specify a balance between encoding quality and the time it takes Soundbooth to encode video. • Good Strikes a balance between image quality and the amount of time it takes to encode video. This is the default value. • Best Creates the best possible image quality, but will take substantially longer to encode video. • Speed Specifies that the video be encoded as fast as possible, however, the image will be of lower quality. Recommended for video content used in testing deployments. Closed GOP Every Specifies the frequency of each Closed Group of Pictures (Closed GOP), which cannot reference frames outside of the closed GOP. A GOP consists of a sequence of I, B, and P frames. (This option is available if you choose MPEG-1 or MPEG-2 as the format.) Automatic GOP Placement When selected, sets the placement of Group of Pictures (GOP) automatically. (This option is available if you choose MPEG-1 as the format.) Note: MPEG-1 and MPEG-2 formats include numerous advanced options not listed here. In most cases, selecting a format or preset designed for your target output sets the appropriate options automatically. For detailed information on options not listed, consult the specifications for the MPEG-1 (ISO/IEC 11172) and MPEG-2 (ISO/IEC 13818) formats. Audio export settings In the Export Settings dialog box, the options available in the Audio tab depend on the format you've specified. One or more of these options appear on the Audio tab: Audio Codec or Codec Specifies the codec used to encode the audio data. These options are some of the most commonly used codecs available through Adobe Media Encoder: • AAC (Advanced Audio Coding) A high-quality encoding format supported by many mobile devices. This codec is the default for the H.264 format. • AAC+ Version 1 Uses spectral band replication (SBR) to enhance the compression efficiency in the frequency domain. SBR is a technology that enhances audio codecs, especially at low bit rates and is based on harmonic redundancy in the frequency domain. The audio codec itself transmits the lower and mid-frequencies of the spectrum, while SBR replicates higher frequency content by transposing up harmonics from the lower and mid-frequencies at the decoder. • AAC+ Version 2 This version of the AAC codec couples SBR with Parametric Stereo (PS) to enhance the compression efficiency of stereo signals. The AAC+ Version 2 bit stream is created by down-mixing the stereo audio signal to mono along with Parametric Stereo information used to describe the spatial intensity stereo generation and ambience regeneration at the decoder. By having the Parametric Stereo information coupled with the mono audio stream, the decoder can regenerate a faithful spatial approximation of the original stereo panorama using very low bitrates. • MainConcept MPEG Audio A high-quality encoding format developed by MainConcept, and included with Adobe Premiere Pro, After Effects, and Soundbooth. • PCM (pulse-code modulation) Audio An uncompressed encoding format. Files of this format tend to be larger than files of the other formats. Updated 15 July 2009