FreeDV plus Video

Operating with FreeDV plus Video

Levels and settings for the best audio and video signal

Introduction ·  The Signal ·  Hardware ·  PureSignal ·  Software ·  Operating ·  Technical ·  Contacts


Frequencies for FreeDV plus Video: Primarily on 14236 kHz (shared with FreeDV digital voice)


Detailed procedure: A detailed procedure for setup and adjustments is given in the "FreeDV Plus Doc" PDF document included in the FreeDV plus Video suite software distribution (click on the FreeDV plus Video link on the "Software" page to download the software).

Detailed tutorials and videos for settings for FreeDV are found on the FreeDV webpage (see the FreeDV link on the "Software" page).

Video TX/FreeDV PC: General Settings
Set Windows Mixers for Correct Default Devices
A fine tutorial, "The Ins and Outs of a Sound Card", by Del Schier, K1UHF, was published in the October 2003 QST, pp. 33-36. Although the article focuses on Windows XP, the information applies to later versions of Windows as well.
K1UHF Article Link

From the Windows Control Panel (Sound) Playback mixer, select the TX USB sound card speakers ("Turtle Beach USB Audio" in the author's setup) as the "Default Device" (the TXfftCO5L application's output is applied to the default Playback device).

From the Windows Control Panel (Sound) Recording mixer, select the motherboard sound card microphone ("SoundMAX Integrated Digital HD Audio" in some Windows 7 PC's) as the "Default Device."

Video TX/FreeDV PC: Settings for Digital Voice and Video TX
Set FreeDV for Correct Inputs and Outputs
On the FreeDV GUI, click "Tools", then "Audio Config", and select the devices and sample rates as follows. The name for the author's RX USB sound card ("2- Turtle Beach USB Audio") is shown below. Substitute the name for your RX USB sound card (same entry under "From Radio: Device" and "To Speaker/Headphones"). Select the sample rates (48000). If the Sample Rate list is blank, type in "48000."

Receive
From Radio: Device Sample Rate
USB Sound Card (RX): 2- Turtle Beach USB Audio 48000
To Speaker/Headphones Sample Rate
USB Sound Card (RX): 2- Turtle Beach USB Audio 48000

Click "Apply", then click on the Transmit tab at the bottom. The name for the author's motherboard sound card ("SoundMAX Integrated") is shown below. Substitute the name for your motherboard sound card (same entry under "From Microphone" and "To Radio"). Select the sample rates (48000). If the Sample Rate list is blank, type in "48000."

Transmit
From Microphone Sample Rate
Motherboard Sound Card: SoundMAX Integrated 48000
To Radio Sample Rate
Motherboard Sound Card: SoundMAX Integrated 48000

Click "Apply", then "OK" at the bottom.

Video TX/FreeDV PC: Settings for Receiving Digital Voice with the FreeDV App (screenshot below)
If you're using the older FreeDV v.0.97.1 be sure you've selected the mode ("1400" or "1600") compatible with your FreeDV plus Video software (the "1600" mode is in current use).

Level to FreeDV Encoder: From the Windows Control Panel (Sound) Recording mixer, highlight the RX USB sound card ("2- Turtle Beach USB Audio" for the author's setup), and click the "Properties" button. Click on the "Levels" tab. While receiving a FreeDV plus Video (or FreeDV) signal, with the FreeDV display in Spectrum mode, adjust the mixer Levels "Microphone" slider control low enough so that the spectrum amplitude does not exceed full scale. Received signal strength for both screenshots was S6, as measured on the transceiver's "S" meter.

Speaker Volume: From the Windows Control Panel (Sound) Playback mixer, highlight the RX USB sound card ("2- Turtle Beach USB Audio" for the author's setup), and click the "Properties" button. Click on the "Levels" tab. While receiving a FreeDV plus Video (or FreeDV) signal, adjust the mixer Levels "Speaker" slider control for the desired volume setting.

Tuning (FreeDV plus Video): If you've already tuned the transceiver (receiver) to receive a good quality video image (see the instructions below), no further tuning is required (the AFC in the FreeDV software will lock onto the center FreeDV sub-carrier for proper operation).

Tuning (FreeDV alone without video): The transceiver (receiver) is tuned so that the center sub-carrier of the received FreeDV signal is at the 1500 Hz mark on the spectrum (or waterfall) display. This setting needs not be exact, as the FreeDV software incorporates an AFC feature to lock on to the center sub-carrier.

Squelch: The Squelch slider should be set low enough to avoid missing syllables and high enough to avoid digital ("R2D2") noise in decoding. The author sets the Squelch slider at 4 to eliminate the loud "pop" received when the other station begins its transmission.

SNR: Signal-to-noise peaks of 10-14 should be expected with FreeDV plus Video operation with strong (S6 or greater) signals. Without video, (FreeDV alone), SNR readings of 15-17 should be obtained.

Video TX/FreeDV PC: Settings for Transmitting Digital Voice with the FreeDV App (screenshot below)
Mic level: From the Windows Control Panel (Sound) Recording mixer, select the motherboard sound card microphone input ("SoundMAX Integrated Digital HD Audio" in some Windows 7 PC's) as the "Default Device." Highlight the motherboard sound card microphone input and click the "Properties" button. Click on the "Levels" tab. While speaking into the mic, after clicking the PTT button, adjust the mixer Levels "Microphone" slider control so that the voice peaks on the FreeDV screen are about 60% of full scale. No further adjustment of this setting should be necessary, so the Windows Record (Microphone) mixer control can be closed (for normal operation, it will not need to be re-opened).

Power sharing adjustment: Two level slider controls are used to set the amplitude of the FreeDV sub-carriers with respect to the video sub-carrier amplitude. This adjustment ensures minimum IM products and reduced noise in the received video. Both the FreeDV and TXfftCO5L applications are opened while making these adjustments. The transceiver is keyed to the TX mode using the PTT button on the FreeDV application.
TX LEVEL 1 (on "Software" page Setup diagram): From the Windows Control Panel (Sound) Playback mixer, highlight the motherboard sound card speakers output ("SoundMAX Integrated Digital HD Audio" in some Windows 7 PC's) and click the "Properties" button. Click on the "Levels" tab. Mute the "Line In" and "PC Beep" functions. Set the Levels "Speaker" slider control to "20."

TX LEVEL 2 (on Setup diagram): From the Windows Control Panel (Sound) Record mixer, highlight the TX USB sound card ("Turtle Beach USB Audio" in the author's setup) microphone input, and click the "Properties" button. Click on the "Levels" tab. Set the Levels "Microphone" slider control so that the amplitude of the center FreeDV sub-carrier (as viewed on the FreeDV RX spectrum display with an in-shack monitor receiver or as monitored by another station) is just below the surrounding video sub-carriers (a setting of "25" on the author's setup). The FreeDV Spectrum display should be similar to the Video TX/FreeDV PC screenshot below.
Adjust transceiver output power level: Both the FreeDV and TXfftCO5L applications are opened while making this adjustment. The transceiver is keyed to the TX mode using the PTT button on the FreeDV application.
TX LEVEL 3 (on Setup diagram): From the Windows Control Panel (Sound) Playback mixer, select the TX USB sound card ("Turtle Beach USB Audio" in the author's setup) speakers output as the "Default Device." Highlight the TX USB sound card speakers output and click the "Properties" button. Click on the "Levels" tab. The Levels "Speakers" slider control is used to set the level of the baseband FreeDV plus Video signal to the transceiver audio input. This setting is made while monitoring the average output power from the transceiver. This level is set to about 1/6 the transceiver rated output power (15-20 watts average power out for a 100-watt transceiver).

Video TX/FreeDV PC: Settings for Transmitting Video with the TXfftCO5L App (screenshot below)
Live webcam video: From the menu, USB webcam "live" video can be selected to be transmitted along with voice. A flashing yellow rectangle is displayed to show the portion of the webcam image actually transmitted. The image is sampled at only 1 frame/sec, so any motion in the received live video will be "jerky" (not smooth). The operator and shack should be well-lighted for good video quality (the author uses a Woods 860-151 8.5 inch diameter, 40 W., clamp light clamped to a shelf on the computer cabinet -- the computer cabinet houses the computers and radio).

AVI Video clips: From the menu, AVI video clips can be selected to be transmitted along with voice. The .AVI file should be located in the same folder as the TXfftCO5L application. Although the image is sampled at only 1 frame/sec, the received video can be recorded for later playback at 10 frames/sec (with smooth, natural motion). But remember that 18 seconds of smooth 10 frames/sec playback will require receiving a transmission for 3 full minutes! Note that only video can be recorded (not voice). The screenshot shows the receiving station ready to send the Microsoft WNDSURF1.AVI test file (the title frame is displayed in the screenshot). Mouse over the screenshot to enlarge.

Click on the link below to download the WNDSURF1.AVI test file. Look for and select AVISAMPL.EXE (WNDSURF1.AVI, along with another AVI file SAMPLE.AVI, is unzipped when AVISAMPL.EXE is opened). Keep this test file in the same folder as the TXfftCO5L application.
AVI Test File Link

Text "crawl": From the menu, a text "crawl" may be selected to be displayed at the bottom of the transmitted image. The "crawl" text is taken from the TESTPATT.ini file included with the software. An ASCII text editor (i.e., Notepad) can be used to edit the TESTPATT.ini file, substituting your text, up to 255 characters. This feature works best with Windows XP.

Video RX PC: Scroll down further for settings for the Video RX PC software.


Screenshot of Video Tx/FreeDV PC running FreeDV and TXfftCO5L software (Windows XP)

Video RX PC: General Settings
From the Windows Control Panel (Sound) Recording mixer, select the motherboard sound card microphone input ("Realtek HD Audio" in some Windows Vista PC's) as the "Default Device" (the RXfftDIFF7L application receives its input from the default device).

Video RX PC: Settings for Receiving Video with the RXfftDIFF7L and WinWarbler Apps (screenshot below)
Levels
A screenshot for the Video RX PC is shown below (mouse over the screenshot to enlarge).

In WinWarbler, click the "Config" button, and select the "Soundcard" tab. For both the "PSK soundcard" and "Phone soundcard", select the radio buttons for the motherboard sound card microphone input ("Realtek HD Audio" for some Windows Vista PC's). Close the "WinWarbler Configuration" screen to return to the main WinWarbler screen. On the main WinWarbler screen, select the "AFC" checkbox. These settings will be stored in the WinWarbler application.

From the Windows Control Panel (Sound) Recording mixer, highlight the motherboard sound card microphone input ("Realtek HD Audio" in some Windows Vista PC's) and click the "Properties" button. Click on the "Levels" tab. The Levels "Microphone" slider is used to set the level from the receiver to the RXfftDIFF7L and WinWarbler apps. Set the Levels "Microphone" slider control low enough so the WinWarbler "Receive soundcard overload!" message is not displayed.

Tuning the Video Signal
1. First, the WinWarbler AFC is locked to the B58 sub-carrier (B58 is the video sub-carrier just above the highest FreeDV sub-carrier, shown as a yellow trace in the screenshot). Click anywhere in the top WinWarbler textbox, then click on the B58 sub-carrier on the waterfall. The B58 sub-carrier will begin scrolling down as a yellow trace (depending on signal strength, you may need to repeat until the AFC locks to the B58 sub-carrier). Note that the WinWarbler AFC "Freq" readout indicates 2.174 kHz in the screenshot.

2. If the WinWarbler AFC "Freq" readout is BELOW 2.175 kHz, tune the receiver DOWN in 1 Hz steps until 2.175 kHz is indicated. If the AFC "Freq" readout is ABOVE 2.175 kHz, tune the receiver UP in 1 Hz steps until 2.175 kHz is indicated. Further adjustment may be required to obtain the truest hues in the video image. If the AFC "Freq" readout is low (below 2.175 kHz), the video image will show greenish hues. If the AFC "Freq" readout is high (above 2.175 kHz), the video image will show reddish hues.

3. Unlike the FreeDV software, the RXfftDIFF7L application does not incorporate an AFC feature. So it will be necessary to adjust the receiver tuning slightly to compensate for frequency drift in the other station's transmitter and/or in the local receiver. Both transceivers should be operated in the Split mode so that the receiver is tuned independently of the transmitter (both transmit frequencies should remain unchanged). The AFC in the FreeDV software should easily track the small changes in receiver tuning required to maintain good quality in the video image.

Expect a 4 Hz shift (from 2.175 kHz to 2.171 kHz) in the AFC "Freq" readout when changing from a full-color motion image to an all-black video image (such as when receiving the title frame of WNDSURF1.AVI).

Note that there is a 4-frame latency (delay) of the received video image with respect to the received audio.

Recording Received Video for Playback with the RxReplay7A App (not shown in screenshot)
The RXfftDIFF7L application can be used to record the video portion of the received signal for later playback using the RxReplay7A application. The RXfftDIFF7L application records the received video as a file in ".49" format. For playback, the ".49" file should be located in the same folder as the RxReplay7A application. The recording feature is especially useful when an .AVI video clip has been transmitted at 1 frame/sec, because RxReplay7A will permit playback at 10 frames/sec. Thus a received AVI clip can be played back with smooth motion.

Processing Recorded Video
The RxReplay7A application can only play back ".49" video files. Each frame of the ".49" file is sent to the Windows Clipboard as it is displayed.

If live video is recorded to a ".49" file, the jerky 1 frame/sec video can be processed into smooth 10 frames/sec video using special software. The author uses AVI Constructor to convert the ".49" file, sent frame-by-frame to the Clipboard from RxReplay7A, to an .AVI file. Then MotionPerfect is used to provide frame interpolation, converting the 1 frame/sec .AVI file to another .AVI file at 10 frames/sec. Click on the links below for more information and downloads of demo software for AVI Constructor and MotionPerfect.
AVI Constructor Link - - MotionPerfect Link - - MotionPerfect Demo Video

Photos of a typical FreeDV plus Video station setup: Scroll down further for photos of a station operating FreeDV plus Video.


Screenshot of Video RX PC running RXfftDIFF7L and WinWarbler software (Windows Vista)

Typical Setup for FreeDV plus Video (photos below: mouse over photo to enlarge)
Top: The laptop PC's and the ANAN-10E SDR transceiver at WA6NUT.

Middle: The directional coupler and adjustable RF attenuator are used with PureSignal. The Omni VII is used to monitor the transmitted audio and video.

Bottom: The RF amplifier deck (the Ameritron AL-811 is driven from the HF Packer). The AL-811 feeds a Cushcraft MA5B beam at 30 feet.






















- 5 July 2013 -

Back to WA6NUT home page