The audio tab includes all settings related to the audio processing of the encoded file.
The audio codec pulldown menu sets the target format of the converted file's audio stream. The audio format is handled by the currently selected encoding engine (each engine doesn't handle all formats). The following choices are currently available:
This popular format is normally used as audio stream for DivX and XviD movies. It is not used for MPEG-1 and MPEG-2. By selecting "ffmpeg Passthrough" as video codec and disabling "Encode video", you can convert an input movie with a WAV, AC3 or MP2 audio track to a MP3 file. By also selecting "invert mapping" you can convert a WAV, AC3 or MP2 file to an MP3 file. ffmpeg and mencoder engines use the "lame" Unix encoder to create MP3 streams. MP3 CBR is used, as AVI doesn't handle very well MP3 VBR. mpeg2enc engine doesn't support MP3 encoding.
This audio format is used for MPEG-1 and MPEG-2. By selecting "ffmpeg Passthrough" as video codec and disabling "Encode video", you can convert an input movie with a WAV, AC3 or MP3 audio track to an MP2 file. By also selecting "invert mapping" you can convert a WAV, AC3 or MP3 file to an MP2 file. ffmpeg engine uses its own super-fast mp2 encoder. mencoder engine doesn't support mp2. mpeg2enc engine uses the mp2enc Unix encoder to create mp2 streams.
This audio format is used for MPEG-2 DVDs, though some DivX also use an AC3 audio stream. mencoder engine can also use AC3 but just by passing it through" from the source movie (typically from a VOB file).
Choose this setting when you don't want to re-encode the audio stream, but just pass it through and copy it into the destination file.
This low quality audio format should be used to encode audio in 3GP containers for playback in smart phones and handheld devices. It is optimized to compress audio at extremely low bitrates.
This audio format should be used when encoding to DV Video.
This audio format, part of the MPEG-4 specifications, is the actual "state of the art" in audio coding. It provides an audio quality at 96 kbps which is slightly better than MP3 at 128 kbps and MP2 at 192 kbps. This format should be used when encoding to MOV mpeg-4, MOV XviD or 3GP. It is not compatible with AVI containers (use MP3 or AC3 for these).
Use this control to enable or disable the audio encoding. Useful when you just want to convert the video (currently supported with ffmpeg engine only).
Sets the audio bitrate in kbit/sec. Popular values are 128 for MP3, 224 for MP2 and 448 for AC3. The audio bitrate is taken into account by the bitrate calculator (video tab).
Sets the audio sampling rate in Hz. Popular values are 48000 for DVD, 44100 for VCD and SVCD. In some cases, if you obtain audio sync problems, prefer to use an audio sampling rate matching the source material.
Sets stereo, mono or 5:1 (for AC3) channels encoding.
Defines mp3 encoding profile for mencoder mpeg-4 and XviD encoding. Available modes are CBR (Constant Bitrate, default), ABR (Average Bitrate) and VBR (Variable Bitrate, uses the optimal q=2 quantization level). (Not available for mp2 encoding or ffmpeg engine).
Sets the audio gain for mencoder engine. Allowed values are 0..+9.
Normalize audio level by analyzing the whole input audio track and automatically adjusting the volume for the best average value before re-encoding it, so as to avoid volume too low or clipping. Currently available with ffmpeg mpeg-2, ffmpeg mpeg-1, and mpeg2enc without "Decode with mplayer". (For mencoder engine DivX/XviD/h.264, you may use the Audio "Gain" popup to manually adjust the encoded volume).
Sets the audio track for multiple-track audio sources. When opening a non-encrypted VIDEO_TS folder, the list of available audio streams is automatically shown in the popup menu. If the source is a non-encrypted VOB, you must set this popup menu according to the value of the input audio track (0-7). Audio track number selection is also applicable to Quicktime and AVI files containing multiple audio tracks.
Enable this checkbox to handle input files having inverted streams ie audio first and video second. Supported by ffmpeg engine only. When encoding from an audio-only file, you must check this box.
Use another file as audio source for the encoded movie. Currently supported by ffmpeg engine only.