What I did to get analog tv tuner, composite, or s-video capture to work:

1. Fresh install of mythbuntu 9.04
2. Extract and install the firmware files for HVR-1950:
   1. Download http://www.isely.net/downloads/fwextract.pl to ~/Desktop
   2. Insert the CD that came with your HVR-1950 (contains windows drivers) [assume it mounted as /media/cdrom0]
   3. cd ~/Desktop
   4. chmod u+x fwextract.pl
   5. ./fwextract.pl /media/cdrom0/Drivers/
   6. sudo copy *.fw /lib/firmware
3. Run mythtv-setup using sudo
   1. sudo mythtv-setup
   2. Capture Card Type: IVTV MPEG-2 encoder card
   3. Video device: /dev/video0
   4. Probed info: WinTV HVR-1950 Model Category 7 [pvrusb2]
4. Run mythtvfrontend
5. (if the video looks really bad in mythfrontend):
   1. Utilities/Setup
   2. Setup
   3. TV Settings
   4. Recording Profiles
   5. MPEG-2 Encoders (PVR-x50, PVR-500)
   6. for Live TV, Default, High Quality, Low Quality
      1. Change Width to 720
      2. Change Height to 480

Notes:

• To use it for digital capture instead of analog I think you need to use the DVB DTV capture card type.
• If you do not run mythtv-setup through sudo you will get an error message: “Probed info: Failed to open” and “Could not open ‘/dev/video0′ to probe its inputs.”
• If you do not extract and install the firmware files, then the HVR-1950 usb will not init.  You should get the following files extracted and copied: v4l-cx2341x-enc.fw, v4l-cx25840.fw, v4l-pvrusb2-29xxx-01.fw, v4l-pvrusb2-73xxx-01.fw
• If you try to do this on MythBuntu 8.10 you will run into the deadlock problem described in http://www.isely.net/pvrusb2/history.html and fixed in the pvrusb2-mci-20081019 release.  (I did not try to recompile the pvrusb2 driver in 8.10 because I assume it is part of the kernel and it seemed like a lot of work.  If you do and it works, let me know how.)
• My research shows that MythBuntu does not use the standalone pvrusb2 driver but uses the -in V4L version thus further complicating the compiling of an up-to-date version of pvrusb2.  I also could not figure out which packages to force upgrade in order to get the latest pvrusb2.
• Some things I did that I don’t think helped fix the problems:
  • sudo apt-get update
  • sudo apt-get dist-upgrade
  • sudo apt-get autoremove
  • sudo rmmod pvrusb2
  • sudo modprobe pvrusb2
• If you find this information useful you might also find a useful ad on my site and click to read more about it. 

References:

• http://www.mythbuntu.org/
• http://www.isely.net/pvrusb2/pvrusb2.html
• http://ubuntuforums.org/showthread.php?p=6732655#post6732655
• http://www.linuxtv.org/wiki/index.php/ATSC_USB_Devices

dmesg output should be something like this when the device is connected properly:

[ 3014.636441] usbcore: registered new interface driver pvrusb2
[ 3014.636450] pvrusb2: V4L in-tree version:Hauppauge WinTV-PVR-USB2 MPEG2 Encoder/Tuner
[ 3014.636456] pvrusb2: Debug mask is 31 (0x1f)
[ 3015.636130] usb 5-6: firmware: requesting v4l-pvrusb2-73xxx-01.fw
[ 3015.647622] pvrusb2: Device microcontroller firmware (re)loaded; it should now reset and reconnect.
[ 3015.679396] usb 5-6: USB disconnect, address 5
[ 3015.679836] pvrusb2: Device being rendered inoperable
[ 3017.432020] usb 5-6: new high speed USB device using ehci_hcd and address 6
[ 3017.573844] usb 5-6: configuration #1 chosen from 1 choice
[ 3017.670711] cx25840' 0-0044: cx25843-24 found @ 0x88 (pvrusb2_a)
[ 3017.703925] tuner' 0-0042: chip found @ 0x84 (pvrusb2_a)
[ 3017.727963] tveeprom 0-00a2: Hauppauge model 75111, rev C3E9, serial# 5371008
[ 3017.727968] tveeprom 0-00a2: MAC address is 00-0D-FE-51-F4-80
[ 3017.727972] tveeprom 0-00a2: tuner model is Philips 18271_8295 (idx 149, type 54)
[ 3017.727976] tveeprom 0-00a2: TV standards NTSC(M) ATSC/DVB Digital (eeprom 0x88)
[ 3017.727979] tveeprom 0-00a2: audio processor is CX25843 (idx 37)
[ 3017.727982] tveeprom 0-00a2: decoder processor is CX25843 (idx 30)
[ 3017.727985] tveeprom 0-00a2: has radio, has IR receiver, has IR transmitter
[ 3017.727992] pvrusb2: Supported video standard(s) reported available in hardware: PAL-M/N/Nc;NTSC-M/Mj/Mk;ATSC-8VSB/16VSB
[ 3017.727998] pvrusb2: Mapping standards mask=0x300b700 (PAL-M/N/Nc;NTSC-M/Mj/Mk;ATSC-8VSB/16VSB)
[ 3017.728016] pvrusb2: Setting up 6 unique standard(s)
[ 3017.728023] pvrusb2: Set up standard idx=0 name=PAL-M
[ 3017.728026] pvrusb2: Set up standard idx=1 name=PAL-N
[ 3017.728029] pvrusb2: Set up standard idx=2 name=PAL-Nc
[ 3017.728033] pvrusb2: Set up standard idx=3 name=NTSC-M
[ 3017.728036] pvrusb2: Set up standard idx=4 name=NTSC-Mj
[ 3017.728039] pvrusb2: Set up standard idx=5 name=NTSC-Mk
[ 3017.728042] pvrusb2: Initial video standard (determined by device type): NTSC-M
[ 3017.731049] pvrusb2: Device initialization completed successfully.
[ 3017.731131] pvrusb2: registered device video0 [mpeg]
[ 3017.731135] DVB: registering new adapter (pvrusb2-dvb)
[ 3017.757981] cx25840' 0-0044: firmware: requesting v4l-cx25840.fw
[ 3019.986050] cx25840' 0-0044: loaded v4l-cx25840.fw firmware (16382 bytes)
[ 3020.168547] tda829x 0-0042: setting tuner address to 60
[ 3020.192529] tda18271 0-0060: creating new instance
[ 3020.228545] TDA18271HD/C1 detected @ 0-0060
[ 3021.424529] tda829x 0-0042: type set to tda8295+18271
[ 3024.742477] cx25840' 0-0044: Video signal: not present
[ 3024.742482] cx25840' 0-0044: Detected format: NTSC-M
[ 3024.742485] cx25840' 0-0044: Specified standard: NTSC-M
[ 3024.742487] cx25840' 0-0044: Specified video input: Composite 7
[ 3024.742490] cx25840' 0-0044: Specified audioclock freq: 48000 Hz
[ 3024.749349] cx25840' 0-0044: Detected audio mode: mono
[ 3024.749353] cx25840' 0-0044: Detected audio standard: no detected audio standard
[ 3024.749356] cx25840' 0-0044: Audio muted: no
[ 3024.749359] cx25840' 0-0044: Audio microcontroller: detecting
[ 3024.749362] cx25840' 0-0044: Configured audio standard: automatic detection
[ 3024.749365] cx25840' 0-0044: Configured audio system: BTSC
[ 3024.749367] cx25840' 0-0044: Specified audio input: Tuner (In8)
[ 3024.749370] cx25840' 0-0044: Preferred audio mode: stereo
[ 3024.808916] cx25840' 0-0044: firmware: requesting v4l-cx25840.fw
[ 3027.024318] cx25840' 0-0044: loaded v4l-cx25840.fw firmware (16382 bytes)
[ 3029.267787] usb 5-6: firmware: requesting v4l-cx2341x-enc.fw
[ 3029.508914] cx25840' 0-0044: 0x0000 is not a valid video input!
[ 3031.787749] DVB: registering adapter 0 frontend 0 (Samsung S5H1411 QAM/8VSB Frontend)...
[ 3031.790123] tda829x 0-0042: type set to tda8295
[ 3031.828013] tda18271 0-0060: attaching existing instance