$ ./ffmpeg/ffmpeg -v 99 -framerate 24 -s vga -f video4linux2 -i /dev/video0 http://127.0.0.1:8001/webcam-webm.ffm
ffmpeg version N-35110-g0b9a69f, Copyright (c) 2000-2011 the FFmpeg developers
  built on Nov 23 2011 11:19:21 with gcc 4.6.1
  configuration: --enable-encoder=mpeg1video --enable-decoder=mjpeg --enable-postproc --enable-libvpx --enable-ffserver
  libavutil    51. 26. 0 / 51. 26. 0
  libavcodec   53. 37. 0 / 53. 37. 0
  libavformat  53. 21. 0 / 53. 21. 0
  libavdevice  53.  4. 0 / 53.  4. 0
  libavfilter   2. 49. 0 /  2. 49. 0
  libswscale    2.  1. 0 /  2.  1. 0
[video4linux2,v4l2 @ 0x2649ae0] [3]Capabilities: 5000001
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x32315559 to 0x4745504A
    Last message repeated 1 times
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x50323234 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x56595559 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x59565955 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x50313134 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x39565559 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x4F424752 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x50424752 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x33524742 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x33424752 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x34524742 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x59455247 to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x3231564E to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver changed the pixel format from 0x47504A4D to 0x4745504A
[video4linux2,v4l2 @ 0x2649ae0] The V4L2 driver set input_id: 0, input: zc3xx
[video4linux2,v4l2 @ 0x2649ae0] Setting time per frame to 1/24
[mjpeg @ 0x2650420] err{or,}_recognition separate: 1; 1
[mjpeg @ 0x2650420] err{or,}_recognition combined: 1; 65537
[mjpeg @ 0x2650420] Unsupported bit depth: 0
[mjpeg @ 0x2650420] buffer too small, expanding to 33005 bytes
[mjpeg @ 0x2650420] marker=d8 avail_size_in_buf=33005
[mjpeg @ 0x2650420] marker parser used 0 bytes (0 bits)
[mjpeg @ 0x2650420] marker=db avail_size_in_buf=33003
[mjpeg @ 0x2650420] index=0
[mjpeg @ 0x2650420] qscale[0]: 4
[mjpeg @ 0x2650420] index=1
[mjpeg @ 0x2650420] qscale[1]: 8
[mjpeg @ 0x2650420] marker parser used 132 bytes (1056 bits)
[mjpeg @ 0x2650420] marker=c4 avail_size_in_buf=32869
[mjpeg @ 0x2650420] class=0 index=0 nb_codes=12
[mjpeg @ 0x2650420] class=0 index=1 nb_codes=12
[mjpeg @ 0x2650420] class=1 index=0 nb_codes=251
[mjpeg @ 0x2650420] class=1 index=1 nb_codes=251
[mjpeg @ 0x2650420] marker parser used 418 bytes (3344 bits)
[mjpeg @ 0x2650420] marker=c0 avail_size_in_buf=32449
[mjpeg @ 0x2650420] sof0: picture: 640x480
[mjpeg @ 0x2650420] component 0 2:1 id: 0 quant:0
[mjpeg @ 0x2650420] component 1 1:1 id: 1 quant:1
[mjpeg @ 0x2650420] component 2 1:1 id: 2 quant:1
[mjpeg @ 0x2650420] pix fmt id 21111100
[mjpeg @ 0x2650420] marker parser used 17 bytes (136 bits)
[mjpeg @ 0x2650420] escaping removed 85 bytes
[mjpeg @ 0x2650420] marker=da avail_size_in_buf=32430
[mjpeg @ 0x2650420] component: 0
[mjpeg @ 0x2650420] component: 1
[mjpeg @ 0x2650420] component: 2
[mjpeg @ 0x2650420] marker parser used 32344 bytes (258749 bits)
[mjpeg @ 0x2650420] marker=d9 avail_size_in_buf=0
[mjpeg @ 0x2650420] mjpeg decode frame unused 0 bytes
[video4linux2,v4l2 @ 0x2649ae0] All info found
[video4linux2,v4l2 @ 0x2649ae0] Estimating duration from bitrate, this may be inaccurate
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 246301.143232, bitrate: N/A
    Stream #0:0, 1, 1/1000000: Video: mjpeg, yuvj422p, 640x480, 1/24, -4 kb/s, 24 tbr, 1000k tbn, 24 tbc
[ffm @ 0x264bec0] Format ffm probed with size=2048 and score=101
[buffer @ 0x2649800] w:640 h:480 pixfmt:yuvj422p tb:1/1000000 sar:0/1 sws_param:
[buffersink @ 0x264da60] auto-inserting filter 'auto-inserted scale 0' between the filter 'src' and the filter 'out'
[scale @ 0x264e260] w:640 h:480 fmt:yuvj422p -> w:640 h:480 fmt:yuv420p flags:0x4
[mpeg1video @ 0x264f9a0] codec type or id mismatches
Output #0, ffm, to 'http://127.0.0.1:8001/webcam-webm.ffm':
    Stream #0:0, 0, 1/1000000: Video: vp8, yuv420p, 640x480, 1/24, q=2-31, 512 kb/s, 1000k tbn, 24 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg -> mpeg1video)
Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height