faq_wave_e - DTXMania Wiki - DTXMania

Editing WAVE file

Outline

How to make preview sound?

Here is a general flow;

Prepare the song file by WAV file.
Cut off the climax part of the song.
Add fade-in-effect to the head of the (b). And also add fade-out-effect to the tail of the (b).
Add silence to the tail of (c). (This FAQ author tend to add 0.6sec silence)

Here is the example way to do the step (b)-(d) by using Audacity.

1. At first, open the song file by Audacity. Then, cut-off the non-climax part a little by little, like the figure below. (Choose the deleting part by dragging, then push "Delete" to delete that part). This figure shows that deletes the long-tail-part. Usually, the first delete will be the big one, and second/third... deletion become smaller. To delete small part, it's useful to enlarge the display of wave, by Ctrl+MouseWheel.

2. As the result of 1., the climax part of the song remains. Next, select the head of the climax-part "a little" by dragging, then click "Effect"-"Fade In".

3. And also, select the tail of the climax-part "longer" (about 2-4 seconds), then click "Effect"-"Fade Out". The figure below shows the result.

4. Add silence to the tail of the data. First. click any part of the wave to release the selection. Next, click the tail of the wave to set the silence-insertion-position to the tail. Then click "Generate" - "Silence".

5. "Silence" dialog appears. First you choose the duration menu to "hh:mm:ss + milliseconds" to specify millisecond value easier.

6. Then set "00h 00m 00.600s" to insert 600ms-silence, and click "OK".

7. 0.6second-silence is added to the tail of the wave.

8. At last, save the a wave file. Save it by "File" - "Export". You can choose "Export as WAV" or "Export as OGG". If you may edit the file later, you should save it as WAV. If not, you should save it as OGG.

What is Normalize?

For example, 16bit-wave data can use the value of -32768-32767. However, usually, practical data does not use all range of -32768-32768. (ex. -8000-5000, etc)

The actual range depends on each wave data, but anyway the amplitude means the volume. So, as the result, "Each song data has different volumes."

To prevent it, all wave data should use all range (-32768-32767). This operation is usually called as "Normalize." You can do it in Audacity by "Effect" - "Normalize".

Normalized song data's volumes are almost all the same.

# However, in real, normalized data have different sound pressure, so you'll feel the different volume. To match the volume of your feeling, you should use "Effect" - "Compressor" to match sound pressure to other sounds.

Petit noise occurs at the tail of the sound. How to remove it?

The cause of petit-noise at the tail of the sound is, "suddenly change the volume at the tail of the sound".

The figure below show the typical case which occurs the petit noise at the tail of the wave. The last value of the big, and when the playback ends, the value become zero. Big value become zero drastically. This is the cause of the noise.

Typical case to cause the noise at the tail of the sound. The bigger the last value of the wave is ... the bigger the noise is.

To solve it, set the last value near zero. To realize it, you can choose 2 ways;

Search the zero-cross-point near the tail of the sound, and set it to the tail. ( = cut off the rest of data)
Set "Fade Out" effect to the tail part.

Here is the step to do the second way by Audacity.

Choose the tail of the wave "a little".
Click "Effect" - "Fade Out".

Example to set Fade-Out to the tail of the wave. The value of tail of wave are smoothly become zero. So the noise does not occur. BTW unexpectedly selected area begins from zero-cross-point. In this case you can solve the noise issue by "Deleting" the selected area instead of "Fade-Out".

After cut-and-paste the waveform, petit-noise occurs. How to prevent it ?

When you cut-and-paste the waveform, both beginning/terminating point must be "zero crossing point"

"Zero crossing point" means the point which the value become "minus -> plus" or "plus -> minus". Shortly to say "crossing the zero".

Typical zero crossing points.

If you cut the waveform from/to the zero crossing points, the big difference of value does not occur near the cut-off points. As the result, drastic change of value does not happen....it means no noise happens.

In Audacity, you can use "At Zero Crossings" feature. First roughly choose the area, then click "Select" - "At Zero Crossings". As the result, selected point (from/to) become zero-crossing point".