General information

Q.1> how can i change biterate in audacity?

Q.2> If i change biterate,sample rate and audio codec like ac3,aac from wave,mpeg4,mp3 or any other than audio get unsync from video?

Q.3> i have underworld movies in bluray with aac or ac3 audio and other movies of same title in xvid and dvdrip. I extract audio frm dvdrip and other audio frm bluray and both import in audacity. Dvdrip is short in length and unsync,now which function of audacity helpful to me for solve this task?

There is no such thing. If you mean bit rate of a compressed audio format like AAC or MP3, in the export window, select the format you want to export to then click “Options…” (bottom right). See: Audacity Manual .

You may have to change the delay in the audio if you export to lossy formats like AAC and MP3. These typically add a little silence padding to the start of the audio. The lossy encoding does not change the speed of the audio.

This is the third time I have given you this answer. Effect > Change Speed. See: Audacity Manual .


Change of speed chage audio quality also, audio changed very badly.

I tried from change tempo and it works audio quality is better than before
But i just want to kmow can i adjust two eng and hindi audio by sync waveform pattern because audio gets unsync many places
And can you suggest how much change speed value should be adjusted?

Change of speed barely changes the audio quality at all. It speeds up or slows down the audio, like changing the speed of a cassette tape or record. It does change the pitch. Speeding it up makes it sound “higher” and slowing it down makes it sound “lower”.

No. Changing tempo does not change the pitch. This is “un-natural” and necessarily damages the audio quality as it is “stretched” or “squashed” to fit the same pitch.

All you mean is that the pitch does not change.

As already suggested, make the Hindi audio the same length as the English audio. Then when the delay is adjusted the audio will not drift out of synchronisation with the video.

We cannot see your computer.

If you are not sure how long the English audio is, install FFmpeg . Then drag the video file that has the English audio into Audacity. This will import the audio of the video into Audacity. Click above Mute / Solo to left of the blue waves to select all the audio. Then if you look in Selection Toolbar at the bottom of the Audacity window, you can see the length of the English audio.

Then import the Hindi audio. I would have expected the Hindi audio would be almost the same length as the English audio. If that was true, then Change Speed would be the best effect to use because you should hardly notice a change of pitch. If the Hindi audio is much shorter or longer than the English audio, it is probably at the wrong pitch anyway.

The simple way to work out what Change Speed to apply is to select the Hindi audio and open Change Tempo. Enter in “Length to” the length of the English audio (the length that you want the Hindi audio to become). The Percent Change box will show you the Percent Change needed. Write down that exact percent change on paper, then cancel Change Tempo.

With the Hindi audio still selected, open Change Speed. Type in the Percent Change that you wrote down and apply the effect.

If the Hindi and English audio are very different lengths and Change Speed changes the pitch in a way you don’t like, then you will have to use Change Tempo. You may get a little bit of unwanted silence with Change Tempo, instead of the audio fitting exactly to the length. If you must use a tempo change effect it may be better to use Sliding Time Scale / Pitch Shift. You can use the same Percent Change that you wrote down, but Time Scale harms the audio quality less than Change Tempo and fits the audio exactly to the requested length.


Hindi audio is 15 minute less
I enter same seconds in hindi audio as in eng audio by change tempo

Ok thanks now i will try as you say

I enter same seconds in length to option of change tempo now hindi audio is two second earlier
Now can u explain in detail in effect> delay’s different option how much value should be type?

I used this change tempo to another movie underworld rise of lycans.
-1st is bluray and 2nd is copy from dvd in xvid
-i extract audio from xvid and import in audacity

  • i used change tempo option and type same amount of sec in length as in eng bluray
    -now after exporting from audacity in ac3 (original xvid in mp3 format)and add audio by avidemux, video kept copy.
    -now hin audio is 1 sec earlier i used shift hin audio of 1 sec delay and export.
    -open this exported video in vlc in start of movie it’s synced but after few seconds it is get out of sync and amount of sync variation get varies or said increase
    So what should i do? How can i sync audio perfectly in whole movie? I did as you said bought dvd from store but as i said bluray is not available here so it is necessary to extract audio from dvd and into bluray.
    And u give me guidance about any option please give me in detail cause i don’t know in which option put how much amount is ideal

And i have man of steel movie of audio format AAC, 48KHZ, OKBPS, STEREO
i made this audio 6 ch(5.1) as posted in audacity now what channel order is ideal because during export audacity show only channel 1 to 6 num
Which channel assign to which number and whaich order is ideal for aac and ac3
And if i i change kbps in new generated 5.1 audio (as mentioned earlier original audio is o kbps) than is this audio get out of sync from video because there is no option for o kbps in audacity
Explain about pitch how to adjust? And for what purpose it used?

I think most of this has been explained if you could re-read what has already been written.

To improve accuracy, you can use the two decimal places for the seconds “Length to” in Change Tempo.

As suggested, use Sliding Time Scale if Change Tempo does not give the correct length or the audio does not fill the length correctly. Enter the same percent change that you used for Change Tempo. Enter that percent change in both the “Initial” and “Final” tempo change.

If you make the Hindi audio the same length as the English audio it cannot drift from the video once the delay has been set, unless the Hindi DVD is a different length to the English BluRay. 15 minutes shorter for Hindi audio is an excessive difference, which makes me think there is something wrong with that Hindi audio, or the Hindi DVD is a shorter version of the film.

If the Hindi audio is synchronised in the DVD, why not simply watch the DVD or burn that Hindi DVD to BluRay?

As I asked before, what post? A post in this Forum?

This has already been explained. You cannot specify channel assignments in Audacity, only move tracks up and down if the exported channel order is not played correctly by the audio player. Click and drag above Mute / Solo to move tracks up or down.

AAC channel order is specified as FC , FL , FR , SL , SR , LFE .

AC3 channel order is not specified but the decoder usually enforces FL , FC , FR , SL , SR , LFE .

There is no such thing as “0 kbps” in a valid audio stream.

Encoding the audio in a lossy format will add silence at the start, which you can adjust using the delay setting in the video player or encoder. Changing the encoding quality or kbps will not further change the length.


Hindi dvd is of low quality video and i have bluray copy of same movie on hard drive and i don’t watch movie on tv it is for computer

That post from topic name: 2 ch to 6 channel

In delay option which amount should be add? I m not proffesional so it is take time for me to understand ok

Audacity does not have a “delay” option, so this is nothing to do with Audacity.


Ok thanks

If the DVD is of “low quality video” and is 15 minutes shorter than the official release, perhaps you should take it back to the shop. If it’s not even the same film as the English version, you will never get the Hindi audio to match with the English video.


Ok thanks gale