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Updated C16 format (markdown)

Erwin Ried 2020-05-30 02:26:57 +02:00
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C16-format.md

@ -1,12 +1,12 @@
The Capture app records into C16 format. Described in the [PortaPack Wiki](https://github.com/sharebrained/portapack-hackrf/issues/139) this format is two channels of 16 bits signed integers. So, the first channel is I and second Q, forming a complex number. You end with three axis for your data, the real, the imaginary and the time (defined by the sample rate).
The Capture app records into C16 files, and the Replay app read those C16. As described in the [PortaPack Wiki](https://github.com/sharebrained/portapack-hackrf/issues/139) this format consist of a tuple of 16 bits signed integers. The first number is I and second Q, forming a complex number. The result, is that you get a tridimensional representation of the capture, the real and the imaginary parts in the file (I and Q), and the time (defined by the sample rate, in this case in an adjacent TXT file with the same filename as the C16).
### Capture manipulation
You can open the C16 file in Audacity importing it as Raw data. Consider the sample rate you used when you captured.
You can open the C16 file in Audacity importing it as _Raw data_. Consider the sample rate you used when you did the capture.
<img src="img/c16_import.png" width="400">
It is possible to manipulate the data as if it was audio. You can apply filters, add silences, trim, mix and merge.
It is possible to manipulate the data as if it was audio. When importing the file as signed 16 bit PCM with two channels, the upper channel contains the I and the second Q, as explained above. You can apply filters, add silences, trim, mix and merge.
<img src="img/c16_export_multitrack.png" width="800">
@ -14,6 +14,12 @@ To export the data as a C16 file, select Export, Export Audio ... and then selec
<img src="img/c16_export.png" width="600">
As a final note, if you created a new file, be sure that the Project Rate matches your capture:
For using the new C16 file in the Replay app, you will also need to include a TXT file with the following metadata (frequency and sample rate):
```
sample_rate=<RATE IN HZ>
center_frequency=<FREQ IN HZ>
```
As a final remark, if you created a new file, be sure that the Project Rate matches your capture:
<img src="img/c16_export2.png" width="300">