logo
Google
 
Home

TMPGEnc Settings (Audio)

The Setting dialog box allows you to alter the encoder parameters. It includes the following tabs:



Audio

Stream type

MPEG-1 specifies 3 "layers" for audio information. They all operate in a similar way, with different levels of complexity in the encoder and decoder. In each the audio is split into 32 sub bands and a psychoacoustic model is applied to decide what audio information can be discarded with the least impact on the listeners perception.

Conventional MPEG decoders can only decode layers 1 and 2, so these are the only ones supported by TMPGEnc. Layer 3 (also known as MP3) encoding and decoding is significantly more complicated. Some decoders support layer 3 audio, but this is not (currently) supported by TMPGEnc.

Choose from:

Type Meaning
MPEG-1 Audio Layer I The simplest MPEG audio format, providing the least compression.
MPEG-1 Audio Layer II Uses previous and next audio frames to provide some simple temporal masking, giving compression benefits over layer 1. For VCD, SVCD and DVD this layer should be used.

Sampling frequency

Select the sampling frequency that you wish to encode to from one of the following options:

Sampling Frequency (Hz) Use
32000 32kHz - Roughly FM radio quality. Use this sampling frequency if you are trying to keep the audio bitrate low. Beware that some DVD players will not play audio streams with 32kHz sampling frequency, so avoid it if you want to avoid compatibility problems.
44100 44.1kHz - CD quality.
48000 48kHz - Better than CD quality.

The average human ear can hear sounds in the frequency range 20-20000Hz. To reproduce a sound at a given frequency the audio sampling rate must be more than twice that frequency. This means that with a sampling frequency of 32000Hz (32kHz) some high frequency information will be lost. The 2 higher sampling frequencies (44100Hz and 48000Hz) have cut-offs above normal human hearing range.

For higher sampling frequencies the audio bitrate must be increased, else the benefit of using the higher sampling frequency will be lost due to an increase in audio artifacts.

Channel mode

Choose from:

Option Use
Stereo The left and right channels are encoded into separate audio streams.
Joint Stereo This mode takes advantage of redundancy between left and right audio channels, increasing the quality at low bitrates. The low frequency information is shared between left and right channels (effectively the channels are mono at low frequencies and stereo at high frequencies) since the human ear cannot determine direction at low frequencies. Dolby surround sound (Prologic) information will be adversely affected by using this option, so if you use a Dolby Prologic decoder, use Stereo mode instead. If your source is not Prologic encoded or you do not want to preserve Prologic information, this option is recommended.
Dual Channel This is similar to Stereo mode except that it indicates that the left and right audio channels contain 2 mono audio signals that are not related. This is used when one languages is encoded on left channel and another language on the right channel.
Mono Only a single audio stream is encoded. Use this if you have a mono source or wish to squeeze the bitrate to the minimum possible and can sacrifice stereo audio.

Bitrate

Select the audio bitrate (in bits per second) from the drop down selection. As a rough guide for layer II stereo audio, 64kbps will give AM radio quality audio, 192kbps will give FM radio quality, 384kpbs will give CD quality audio.

VCD1.0 and VCD1.1 require an audio bitrate of 224kbps. VCD2.0 allows bitrates of 128, 192, 224 or 384 kbps for stereo streams or 64, 96 or 192 kbps for mono streams.

Error protection

Includes CRC checks into the audio data, allowing the decoder to perform error checking. If you are recording to CD, DVD or hard drive, error checking elsewhere in the system makes this option redundant. Use it if you are transmitting using an unreliable media.

Original flag

This is a single bit flag carried in the MPEG audio stream for information only. It does not affect the encoder or decoder. It simply indicates that the material is original.

Copyright flag

This bit indicates that the audio material is protected by copyright. Decoders should look at this bit and not allow the stream to be copied if this bit is set.

Private flag

The private flag can be switched on or off and is not used by the encoder or decoder. In clever systems it could be used to trigger certain events, or even a low data rate stream.

Emphasis

A pre-emphasis filter may have been applied to analogue recorded audio to change the frequency response characteristics. This option indicates that a similar de-emphasis filter should be used in the decoder to reproduce the original audio. With digitally sampled streams this is not necessary, and the emphasis setting should be set to None.


Digital Video
Glossary MPEG Bitrate

Video Editing
Intro

HDTV
Introduction Plasma LCD Projection HDTV Antennas

Freeview
Introduction Aerial Channels Coverage PVR Recording STB Guides TV

Media
VCD SVCD DVD DV

TMPGEnc
Beginners Settings

Encode

Author

MHEG-5

Software

Links

If you have any comments please use the feedback form.
Add to Favourites Privacy Policy
Copyright © 2002-2017 Ian Willis. All rights reserved.