How to amplify the audio in a video file?

Question

What is the simplest way I can amplify the audio in a video file (.avi, .mpg, .flv, etc)?

I transfer these videos and watch them on a portable device (cellphone). Sometimes their audio level is so low that it is barely audible, even when the volume of the player (in the portable device) is turned to the maximum.

(I am using Windows.)

Answer 1

I'll copy my answer from this question

You could use VirtualDub for this. This guide has a short and straight-forward explanation.

Brief:

1. Start VirtualDub and load in your converted DivX file.
2. From the "Video" menu, select "Direct Stream Copy".
3. From the "Audio" menu, select "Full Processing Mode".
4. From the "Audio" menu, select "Volume", check the "Adjust volume of audio channels" option, and you can use the slider to change the level of audio.
5. Press the "Preview Output" button and listen to the audio - if it isn't loud enough, go back to the previous step and increase the amplification level.
6. From the "Audio" menu, select "Compression" and select "MPEG Layer-3" and the same or lower bitrate/attributes (eg. 128 kBit/s, 48000 Hz, Stereo) you used earlier to make the DivX movie.
7. From the "File" menu, select "Save AVI" to save the AVI to include the normalized audio. This shouldn't take too long as only the audio is re-encoded/compressed - the video will be left alone.

Answer 2

You'll need to do this in following steps.

1. Demux (extract) the audio stream from the container, depending on your container you should use the correct application. For a general purpose demuxer you could use ffmpeg. But there are more user friendly programs such as VirtualDub for avi, TMPGEnc for mpg files.
2. Decode the audio to a wave file (not always needed if Audacity can open the file directly)
3. Increase the volume of your audio track using Audacity by gaining your audio file such as described in the first step in this howto.
4. Save the result as a wave file.
5. Encode the wave file using the right tool for your desired audio coded (lame for mp3, faac for aac)
6. Remux the new audio and original video tracks back into the desired container using the same program you used for demuxing.

Answer 3

Very easy to do using ffmpeg:

ffmpeg -i myvideo.avi -vcodec copy -acodec libmp3lame -ab 128k -vol 5000 myvideo_louder.avi

Adjust the "-vol" parameter until you're satisfied with the volume.

While you're looking for the appropriate "-vol" value, I suggest you add a "-t 30" to your commandline, so it'll only process the first 30s of video. It's much faster and should be enough for you to evaluate the results.

Answer 4

Use VirtualDub.

VirtualDub is a video capture/processing utility for 32-bit Windows platforms (95/98/ME/NT4/2000/XP), licensed under the GNU General Public License (GPL). It lacks the editing power of a general-purpose editor such as Adobe Premiere, but is streamlined for fast linear operations over video. It has batch-processing capabilities for processing large numbers of files and can be extended with third-party video filters. VirtualDub is mainly geared toward processing AVI files, although it can read (not write) MPEG-1 and also handle sets of BMP images.

Answer 5

Look at the answers in this question: How to increase the volume for an avi file

(That question seems a duplicate though)