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Data Recording

July 27th, 2016: The program supports recording of the IQ (raw) data to files on your computer which can later be played back. The data is stored using the WAV file format [wikipedia] as this is the de facto standard used by many SDR programs, also the WAV file format is well defined and easy to manipulate with the standard Windows programming API.

When you playback a recording almost all standard features of the software can be used, an example of a feature which is not available is data recording.

This a not an audio recorder - audio recording will be added at a later date.

If the software cannot write fast enough to the hard drive error messages are added to the program's logfile. Now read the Check List (top right of this page).

If you will be writing from two instances of this software at the same time or writing at a high data rate then consider a SSD disk dedicated to recordings. If you do not have a SSD disk then use separate disks for each instance of the console.

 

Recording

Select Recording from the Recording pane in the ribbon bar.

The playback window cannot be opened if a radio is started.

 


Select:

  • The folder where the recording will be stored,
  • The maximum size of each file - if needed more than one file will be created with a unique index starting at 000 (the maximum file size supported by Windows is 2GB),
  • Optionally schedule the recording, the radio must be started and left running if you enable a schedule ( a full scheduler will be added later).

When the recording is running an extra information display is shown on the waterfall:

Note:

  • The sample size is 16-bit (unsigned integer),
  • The storage used for the recording must be capable of a sustained write rate of 4 x the current radio Bandwidth, so if the bandwidth is 1 MHz the write rate will be 4 MB/second.
  • If a high write rate is required use a SSD or SSD array.

 

Playback

To playback a recording select Playback from the Recording pane of the ribbon bar. The Select Recording window is displayed.

The options:

  • Select any folder or a folder from the recently used list, to also search subfolders check [_] Subfolders.
  • To display third-party WAV files (i.e. files which do not have the SDR-Radio.com data block) check [_] 3rd party recordings.
  • To display times in UTC check [_] UTC.
  • If the data is transposed in the frequency axis check [_] Invert spectrum (swaps the I and Q samples).

Press Refresh to update the list.

You can delete any recording files from the displayed list, also you can edit the Info tags for SDR-Radio.com V3 files (more information below).

For an advanced interface select Navigator from the same pane.

3rd-Party Files

All known third-party recording files using the .wav format are supported, for example SpectraVue, Perseus, SDR#.

Info Tags

At present only SDR-Radio.com V3 WAV files contain an Info list of standard fields which are displayed by the Windows Explorer.

The supported fields are: Artist, Album, Comments, Copyright, Title. The title can be edited by selecting Edit Title from the Select Recording window. At present the Info fields cannot be added to recording files which were not created by SDR-radio.com V3, this may be added at a later date.

Exporting Recordings

If you are making a recording to send to another person then follow these steps:

  1. Use a low bandwidth to reduce file size,
  2. Compress the .WAV file(s) with Z-Zip (very good compression ratio),
  3. Upload to Dropbox, OneDrive, Google Drive or similar,
  4. Send the link by e-mail.

Noisy recordings are always welcomed by the developers as they help fine-tune the noise blanker and noise reduction algorithms.

 

 

Check List

Your computer must be able to write to the selected drive at four times the radio bandwidth, so if you have started a NetSDR at 1MHz bandwidth then you must be able to write at 4 megabytes per seconds, in other words four bytes per second for each Hz of bandwidth.

To ensure you can read and write without any problems here are points worth checking:

  • Anti virus software running
  • Windows indexing the contents of the drive
  • Windows defragmenting the drive

Any of the above result in very heavy head movement on traditional spinning hard drives.

Finally make sure your drive actually supports sustained write throughput at the required rate. SSD disks are best.