buggy Import RAW Data

[terrance_h]

Audacity 2.1.3
Ubuntu 16.04 amd64

This also affects windows version.

Importing 16bit signed raw results strange waveform, seems like non linear a-law or u-law. Also most of the raw formats imports result unexpectedly.

Screenshot_2017-04-28_20-38-08.png (85.56 KiB) Viewed 1197 times

attachments:
sin.raw: a signed 16-bit big-endian linear sine wave

[terrance_h]

unable to upload raw file, using this xxd dump instead

[steve]

Note that Audacity attempts to guess the raw data format, but it's no more than an educated guess. It is not possible to make this guess 100% accurate, which is why audio files usually contain header information.

Please test importing this file as RAW data (you can change the file extension if you wish - I've just named it as a WAV file so that I can upload it to the forum).

16-bit_RawDataTest.wav

(344.53 KiB) Downloaded 87 times

The settings should be like this (these are automatically selected on my Xubuntu 16.04 machine):

fullwindow-Import Raw Data-000.png (34.93 KiB) Viewed 1191 times

And this is the (correct) waveform as it appears on my machine after importing as RAW:

firsttrack000.png (9.44 KiB) Viewed 1191 times

[steve]

Importing 16bit signed raw results strange waveform

Not surprising, because "sin.txt" is not 16-bit signed PCM.
Where did that file come from?

[steve]

Here's the first 100 bytes as signed 16-bit big endian:
(it does not look like a sine wave to me)

Code: Select all

0   30 30  12336
2   30 30  12336
4   30 30  12336
6   30 30  12336
8   3A 20  14880
10  65 36  25910
12  30 30  12336
14  20 65  8293
16  39 30  14640
18  30 20  12320
20  65 39  25913
22  30 30  12336
24  20 65  8293
26  62 30  25136
28  30 20  12320
30  65 65  25957
32  30 30  12336
34  20 65  8293
36  66 30  26160
38  30 20  12320
40  66 30  26160
42  30 30  12336
44  20 66  8294
46  33 30  13104
48  30 20  12320
50  20 2E  8238

[terrance_h]

Importing 16bit signed raw results strange waveform

Not surprising, because "sin.txt" is not 16-bit signed PCM.
Where did that file come from?

i cannot upload the raw, the txt is its xxd dump

[terrance_h]

you can "xxd -r " to restore the raw.

the correct waveform is like this (using matplotlib)

Screenshot_2017-04-29_17-27-01.png (60.52 KiB) Viewed 1180 times

[terrance_h]

Note that Audacity attempts to guess the raw data format, but it's no more than an educated guess. It is not possible to make this guess 100% accurate, which is why audio files usually contain header information.

Please test importing this file as RAW data (you can change the file extension if you wish - I've just named it as a WAV file so that I can upload it to the forum).

16-bit_RawDataTest.wav

The settings should be like this (these are automatically selected on my Xubuntu 16.04 machine):

fullwindow-Import Raw Data-000.png

And this is the (correct) waveform as it appears on my machine after importing as RAW:

firsttrack000.png

Thanks! That explains it.

But this is exactly the issue. we need the "Import RAW Data" for raw files have no valid headers. or we can just "open" them.

[terrance_h]

Note that Audacity attempts to guess the raw data format, but it's no more than an educated guess. It is not possible to make this guess 100% accurate, which is why audio files usually contain header information.

Please test importing this file as RAW data (you can change the file extension if you wish - I've just named it as a WAV file so that I can upload it to the forum).

The attachment 16-bit_RawDataTest.wav is no longer available

The settings should be like this (these are automatically selected on my Xubuntu 16.04 machine):

The attachment fullwindow-Import Raw Data-000.png is no longer available

And this is the (correct) waveform as it appears on my machine after importing as RAW:

The attachment firsttrack000.png is no longer available

the attachment is my RAW, extracted from an oscilloscope.

Sometimes I use audacity as a scientific tool, viewing and processing waveform.

[steve]

sin.raw.notrealwav.wav

On my machine, that is detected by Audacity as signed 8-bit, little endian, 2 channel (stereo), which produces this waveform:

firsttrack001.png (19.88 KiB) Viewed 1175 times