Well, kazam now works with the webm format, but the video output is far from perfect.

1) The audio and the video streams are not always very well synchronized.

2) When I try to open the video with Totem, I have this error:
====================================================
Internal GStreamer error: negotiation problem.  Please file a bug at http://bugzilla.gnome.org/enter_bug.cgi?product=GStreamer.
====================================================
I can watch the video only with the gnome sushi files preview


This is the debug log:
==========================================================================================
nicola@pangolino-pb:~$ kazam --debug
DEBUG Kazam - Starting ...
DEBUG Kazam - Running on: Ubuntu 12.04
DEBUG Kazam - Kazam version: 1.3.101-0ubuntu1 NX-01
DEBUG Kazam - Starting new instance ...
DEBUG Constants - Getting hardware specs
DEBUG Constants - Getting Video sources.
DEBUG Constants - Found 1 monitor(s).
DEBUG Constants -   Monitor 0 - X: 0, Y: 0, W: 1366, H: 768
DEBUG Main - Gstreamer version detected: 1.0.4.0
DEBUG Main - Setting variables.
DEBUG PulseAudio - Starting mainloop.
DEBUG PulseAudio - Getting API.
DEBUG PulseAudio - Setting context.
DEBUG PulseAudio - Set state callback.
DEBUG PulseAudio - Connecting to server.
DEBUG PulseAudio - Start mainloop.
DEBUG PulseAudio - State connected.
DEBUG Main - Connecting indicator signals.
DEBUG Main - Starting in silent mode: False
DEBUG Indicator - Indicatior silent: False
DEBUG Indicator - Trying to bind hotkeys.
DEBUG Main - Main Window UI setup.
DEBUG Main - Unable to get name for '<Adjustment object at 0x29db460 (GtkAdjustment at 0x2a1f990)>'

(kazam:8080): Gtk-WARNING **: Can't set a parent on widget which has a parent


(kazam:8080): Gtk-WARNING **: Can't set a parent on widget which has a parent

DEBUG Prefs - Getting Audio sources.
DEBUG PulseAudio - get_audio_sources() called.
DEBUG PulseAudio - pa_sourcelist_cb()
DEBUG PulseAudio -   IDX: 0
DEBUG PulseAudio -   Name: b'alsa_output.pci-0000_00_1b.0.analog-stereo.monitor'
DEBUG PulseAudio -   Desc: b'Monitor of Audio interno Stereo analogico'
DEBUG PulseAudio - pa_sourcelist_cb()
DEBUG PulseAudio -   IDX: 1
DEBUG PulseAudio -   Name: b'alsa_input.pci-0000_00_1b.0.analog-stereo'
DEBUG PulseAudio -   Desc: b'Audio interno Stereo analogico'
DEBUG PulseAudio - pa_sourcelist_cb()
DEBUG PulseAudio -   IDX: 2
DEBUG PulseAudio -   Name: b'alsa_output.usb-Logitech_Logitech_USB_Headset-00-Headset.analog-stereo.monitor'
DEBUG PulseAudio -   Desc: b'Monitor of USB Headset Stereo analogico'
DEBUG PulseAudio - pa_sourcelist_cb()
DEBUG PulseAudio -   IDX: 3
DEBUG PulseAudio -   Name: b'alsa_input.usb-Logitech_Logitech_USB_Headset-00-Headset.analog-mono'
DEBUG PulseAudio -   Desc: b'USB Headset Mono analogico'
DEBUG PulseAudio - pa_sourcelist_cb() -- finished
DEBUG Prefs -  Device found: 
DEBUG Prefs -   - 0
DEBUG Prefs -   - alsa_output.pci-0000_00_1b.0.analog-stereo.monitor
DEBUG Prefs -   - Monitor of Audio interno Stereo analogico
DEBUG Prefs -  Device found: 
DEBUG Prefs -   - 1
DEBUG Prefs -   - alsa_input.pci-0000_00_1b.0.analog-stereo
DEBUG Prefs -   - Audio interno Stereo analogico
DEBUG Prefs -  Device found: 
DEBUG Prefs -   - 2
DEBUG Prefs -   - alsa_output.usb-Logitech_Logitech_USB_Headset-00-Headset.analog-stereo.monitor
DEBUG Prefs -   - Monitor of USB Headset Stereo analogico
DEBUG Prefs -  Device found: 
DEBUG Prefs -   - 3
DEBUG Prefs -   - alsa_input.usb-Logitech_Logitech_USB_Headset-00-Headset.analog-mono
DEBUG Prefs -   - USB Headset Mono analogico
DEBUG Main - Capture cursor: True.
DEBUG Main - Capture speakers: True.
DEBUG Main - Capture microphone: True.
DEBUG Main - Capture cursor_pic: True.
DEBUG Main - Capture borders_pic: True.
DEBUG Main - Preferences requested.
DEBUG Preferences - Preferences Init.
DEBUG Preferences - Preferences UI setup.
DEBUG Preferences - Unable to get name for '<Adjustment object at 0x2bed5f0 (GtkAdjustment at 0x2c290f0)>'
DEBUG Preferences - Unable to get name for '<Adjustment object at 0x2bedb40 (GtkAdjustment at 0x7f2b10003940)>'
DEBUG Preferences - Unable to get name for '<Adjustment object at 0x2beddc0 (GtkAdjustment at 0x2c0db70)>'
INFO GStreamer - Supported encoder: RAW / AVI.
INFO GStreamer - Supported encoder: VP8 / WEBM.
INFO GStreamer - Supported encoder: H264 / MP4.
DEBUG Preferences - Restoring UI.
DEBUG Preferences - Audio Changed.
DEBUG Preferences -   - A_1 0
DEBUG Preferences -   - PA Audio1 IDX: 0
DEBUG PulseAudio - get_source_info_by_index() called. IDX: 0
DEBUG PulseAudio - pa_sourceinfo_cb()
DEBUG PulseAudio -   IDX: 0
DEBUG PulseAudio -   Name: b'alsa_output.pci-0000_00_1b.0.analog-stereo.monitor'
DEBUG PulseAudio -   Desc: b'Monitor of Audio interno Stereo analogico'
DEBUG PulseAudio - pa_sourceinfo_cb() -- finished
DEBUG PulseAudio - pa_sourceinfo_cb() -- Hit EOL
DEBUG PulseAudio - pa_sourceinfo_cb() -- EOL no data!
DEBUG PulseAudio - pa_sourceinfo_cb() -- finished
DEBUG Preferences - Volume 1 changed, new value: 31.059120102247793
DEBUG Preferences - New Audio1: Monitor of Audio interno Stereo analogico
DEBUG Preferences - Audio2 Changed.
DEBUG Preferences -   - A_2 1
DEBUG Preferences -   - PA Audio2 IDX: 3
DEBUG PulseAudio - get_source_info_by_index() called. IDX: 3
DEBUG PulseAudio - pa_sourceinfo_cb()
DEBUG PulseAudio -   IDX: 3
DEBUG PulseAudio -   Name: b'alsa_input.usb-Logitech_Logitech_USB_Headset-00-Headset.analog-mono'
DEBUG PulseAudio -   Desc: b'USB Headset Mono analogico'
DEBUG PulseAudio - pa_sourceinfo_cb() -- finished
DEBUG PulseAudio - pa_sourceinfo_cb() -- Hit EOL
DEBUG PulseAudio - pa_sourceinfo_cb() -- EOL no data!
DEBUG PulseAudio - pa_sourceinfo_cb() -- finished
DEBUG Preferences - Volume 2 changed, new value: 53.99995235126033
DEBUG Preferences - New Audio2:
  USB Headset Mono analogico
DEBUG Preferences - Countdown splash: True.
DEBUG Preferences - Shutter sound: True.
DEBUG Preferences - Shutter type set to: 0 - 
DEBUG Preferences - Codec selected: VP8 / WEBM - 1
DEBUG Preferences - Video folder set to: /home/nicola/Video
DEBUG Preferences - Picture folder set to: /home/nicola/Immagini
DEBUG Preferences - Video folder set to: /home/nicola/Video
DEBUG Preferences - Picture folder set to: /home/nicola/Immagini
DEBUG Preferences - Deleteting preferences window
DEBUG Main - Record clicked, invoking Screencast.
DEBUG GStreamer - audio_source : alsa_output.pci-0000_00_1b.0.analog-stereo.monitor
DEBUG GStreamer - audio2_source : alsa_input.usb-Logitech_Logitech_USB_Headset-00-Headset.analog-mono
DEBUG GStreamer - video_source: {'y': 0, 'x': 0, 'height': 768, 'width': 1366}
DEBUG GStreamer - xid: None
DEBUG GStreamer - area: None
DEBUG GStreamer - Capture Cursor: True
DEBUG GStreamer - Framerate : 15.0
DEBUG GStreamer - Codec: vp8enc
DEBUG GStreamer - Coordinates SX: 0 SY: 0 EX: 1365 EY: 767
DEBUG GStreamer - testing for xid: None
DEBUG GStreamer - Codec: VP8 / WEBM
DEBUG GStreamer - Setup audio elements.
DEBUG GStreamer - Audio1 Source:
  alsa_output.pci-0000_00_1b.0.analog-stereo.monitor
DEBUG GStreamer - Audio2 Source:
  alsa_input.usb-Logitech_Logitech_USB_Headset-00-Headset.analog-mono
DEBUG GStreamer - Filesink: /home/nicola/Video/kazam_9lez5_.movie
DEBUG GStreamer - Linking Video
DEBUG GStreamer - Linking Audio
DEBUG GStreamer -  Link audiosrc -> aud_in_queue: True
DEBUG GStreamer -  Link aud_in_queue -> aud_caps_filter: True
DEBUG GStreamer - Linking Audio2
DEBUG GStreamer -  Link aud_caps_filter -> audiomixer: True
DEBUG GStreamer -  Link audio2src -> aud2_in_queue: True
DEBUG GStreamer -  Link aud2_in_queue -> aud2_caps_filter: True
DEBUG GStreamer -  Link aud2_caps_filter -> audiomixer: True
DEBUG GStreamer -  Link audiomixer -> audioconv: True
DEBUG GStreamer - Link audioconv -> audioenc: True
DEBUG GStreamer - Link audioenc -> aud_out_queue: True
DEBUG GStreamer - Link aud_out_queue -> mux: True
DEBUG GStreamer - Link mux -> file queue: True
DEBUG GStreamer - Link file queue -> sink: True
DEBUG Main - Hiding main window.
DEBUG Main - Counter finished.
DEBUG Indicator - Recording started.
DEBUG GStreamer - Setting STATE_PLAYING
DEBUG Indicator - Recording stopped.
DEBUG Main - Stop request.
DEBUG GStreamer - Sending new EOS event
DEBUG Main - Recorded tmp file: /home/nicola/Video/kazam_9lez5_.movie
DEBUG Main - Waiting for data to flush.
DEBUG GStreamer - Received EOS, setting pipeline to NULL.
DEBUG GStreamer - Emitting flush-done.
DEBUG Main - Done Recording initialized.
DEBUG Main - Done recording signals connected.
DEBUG Done Recording - Continue - Save (1).
DEBUG Save Dialog - Save dialog called.
DEBUG Main - Save Done, result: /home/nicola/Scaricati
DEBUG Main - Quit requested.
INFO Main - Unable to delete one of the temporary files. Check your temporary directory.
DEBUG PulseAudio - Disconnecting from server.
DEBUG Kazam - Finishing ...
==========================================================================================