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• Fixing A/V sync issues with RTP/RTCP sent from mediasoup

  10 décembre 2017, par artushin

  A little background : I’m attempting to record a webrtc call being made through the mediasoup v2 SFU. I’m using mediasoup’s room.createRtpStreamer() method to generate a stream which mirrors RTP/RTCP to ffmpeg. Two streamers are created for audio and video within 30ms of each other and begin broadcasting. FFmpeg then spins up and starts accepting. Pretty sure RTCP is working since ffmpeg is always starting with a keyframe despite being started after the streamer begins broadcasting.

  The problem is that I encounter audio/video desynchronization with seemingly random offsets. My current theory is that this offset is based on how old the last keyframe is that RTCP requests to start the stream. See below for ffmpeg configuration and output but my question is : what ffmpeg arguments can I use to adjust the video frame timestamps to match the audio frame timestamps or vice versa ? I’ve messed around with -map 0:0,0:1 -map 0:1,0:1 but it doesn’t seem to do what I’m looking for.

  ffmpeg flags :

  '-y',
  
  '-loglevel',
  
  'debug',
  
  '-dump',
  
  '-protocol_whitelist',
  
  'file,crypto,udp,rtp,data',
  
  '-analyzeduration',
  
  '20M',
  
  '-probesize',
  
  '20M',
  
  '-i',
  
  `data:text/plain;base64,${sdp.toString('base64')}`,
  
  '-fflags',
  
  '+genpts',
  
  '-vcodec',
  
  'copy',
  
  '-acodec',
  
  'aac',
  
  '-bsf:v',
  
  'h264_mp4toannexb',
  
  '-start_number',
  
  '0',
  
  '-hls_list_size',
  
  '2147480000',
  
  '-hls_wrap',
  
  '0',
  
  '-hls_time',
  
  '10',

  SDP used for input (template) :

  v=0
  
  o=- 0 0 IN IP4 <%=ip %>
  
  s=title
  
  c=IN IP4 <%=ip %>
  
  m=audio <%=audioPort %> RTP/AVPF <%=audioPayload %>
  
  a=sendrecv
  
  a=rtcp-mux
  
  a=rtpmap:<%=audioPayload %> opus/48000/2
  
  a=fmtp:<%=audioPayload %> minptime=10; useinbandfec=1
  
  m=video <%=videoPort %> RTP/AVPF <%=videoPayload %>
  
  a=sendrecv
  
  a=rtcp-mux
  
  a=rtpmap:<%=videoPayload %> H264/90000
  
  a=rtcp-fb:<%=videoPayload %> ccm fir
  
  a=rtcp-fb:<%=videoPayload %> nack
  
  a=rtcp-fb:<%=videoPayload %> nack pli
  
  a=rtcp-fb:<%=videoPayload %> goog-remb
  
  a=rtcp-fb:<%=videoPayload %> transport-cc
  
  a=fmtp:<%=videoPayload %> level-asymmetry-allowed=1;packetization-mode=1

  ffmpeg output - garbled with some timestamps

  1512775954585 - stderr: ffmpeg version 3.4 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with Apple LLVM version 9.0.0 (clang-900.0.38)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/3.4 --enable-shared --enable-pthreads --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-gpl --enable-ffplay --enable-libmp3lame --enable-libvpx --enable-libx264 --enable-libxvid --enable-opencl --enable-videotoolbox --disable-lzma
  
  1512775954587 - stderr:   libavutil      55. 78.100 / 55. 78.100
  
    libavcodec     57.107.100 / 57.107.100
  
    libavformat    57. 83.100 / 57. 83.100
  
    libavdevice    57. 10.100 / 57. 10.100
  
  1512775954587 - stderr:   libavfilter     6.107.100 /  6.107.100
  
    libavresample   3.  7.  0 /  3.  7.  0
  
    libswscale      4.  8.100 /  4.  8.100
  
    libswresample   2.  9.100 /  2.  9.100
  
    libpostproc    54.  7.100 / 54.  7.100
  
  Splitting the commandline.
  
  Reading option '-y' ... matched as option 'y' (overwrite output files) with argument '1'.
  
  Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'.
  
  Reading option '-dump' ... matched as option 'dump' (dump each input packet) with argument '1'.
  
  Reading option '-protocol_whitelist' ...1512775954589 - stderr:  matched as AVOption 'protocol_whitelist' with argument 'file,crypto,udp,rtp,data'.
  
  Reading option '-analyzeduration' ...1512775954590 - stderr:  matched as AVOption 'analyzeduration' with argument '20M'.
  
  Reading option '-probesize' ...1512775954590 - stderr:  matched as AVOption 'probesize' with argument '20M'.
  
  Reading option '-i' ... matched as input url with argument 'data:text/plain;base64,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'.
  
  Reading option '-fflags' ...1512775954591 - stderr:  matched as AVOption 'fflags' with argument '+genpts'.
  
  Reading option '-vcodec' ... matched as option 'vcodec' (force video codec ('copy' to copy stream)) with argument 'copy'.
  
  Reading option '-acodec' ... matched as option 'acodec' (force audio codec ('copy' to copy stream)) with argument 'aac'.
  
  Reading option '-vsync' ... matched as option 'vsync' (video sync method) with argument '0'.
  
  Reading option '-map' ... matched as option 'map' (set input stream mapping) with argument '0:0,0:1'.
  
  Reading option '-map' ... matched as option 'map' (set input stream mapping) with argument '0:1,0:1'.
  
  Reading option '-bsf:v' ... matched as option 'bsf' (A comma-separated list of bitstream filters) with argument 'h264_mp4toannexb'.
  
  Reading option '-start_number' ...1512775954591 - stderr:  matched as AVOption 'start_number' with argument '0'.
  
  Reading option '-hls_list_size' ...1512775954591 - stderr:  matched as AVOption 'hls_list_size' with argument '2147480000'.
  
  Reading option '-hls_wrap' ... matched as AVOption 'hls_wrap' with argument '0'.
  
  Reading option '-hls_time' ...1512775954591 - stderr:  matched as AVOption 'hls_time' with argument '10'.
  
  Reading option '/tmp/archive/e0c92fa0-dad5-11e7-8687-090dda95b1a4_10e1c990-dc70-11e7-888d-9f39ca0c79bc/1512775954465.m3u8' ... matched as output url.
  
  Finished splitting the commandline.
  
  Parsing a group of options: global .
  
  Applying option y (overwrite output files) with argument 1.
  
  1512775954592 - stderr: Applying option loglevel (set logging level) with argument debug.
  
  Applying option dump (dump each input packet) with argument 1.
  
  Applying option vsync (video sync method) with argument 0.
  
  Successfully parsed a group of options.
  
  Parsing a group of options: input url data:text/plain;base64,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.
  
  Successfully parsed a group of options.
  
  Opening an input file: data:text/plain;base64,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.
  
  1512775954592 - stderr: [NULL @ 0x7f81fd000000] Opening 'data:text/plain;base64,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' for reading
  
  1512775954593 - stderr: [data @ 0x7f81fca001a0] Content-type: text/plain
  
  {"level":"info","time":"Dec 8, 2017 11:32 PM","message":"ffmpeg started"}
  
  1512775954595 - stderr: [sdp @ 0x7f81fd000000] Format sdp probed with size=2048 and score=50
  
  1512775954598 - stderr: [sdp @ 0x7f81fd000000] audio codec set to: opus
  
  [sdp @ 0x7f81fd000000] audio samplerate set to: 48000
  
  [sdp @ 0x7f81fd000000] audio channels set to: 2
  
  1512775954639 - stderr: [sdp @ 0x7f81fd000000] video codec set to: h264
  
  [sdp @ 0x7f81fd000000] RTP Packetization Mode: 1
  
  [sdp @ 0x7f81fd000000] RTP Profile IDC: 42 Profile IOP: e0 Level: 1f
  
  [udp @ 0x7f81fcb007e0] end receive buffer size reported is 65536
  
  [udp @ 0x7f81fbe00180] end receive buffer size reported is 65536
  
  [sdp @ 0x7f81fd000000] setting jitter buffer size to 500
  
  [udp @ 0x7f81fbe00680] end receive buffer size reported is 65536
  
  [udp @ 0x7f81fbe00740] end receive buffer size reported is 65536
  
  [sdp @ 0x7f81fd000000] setting jitter buffer size to 500
  
  [sdp @ 0x7f81fd000000] Before avformat_find_stream_info() pos: 479 bytes read:479 seeks:0 nb_streams:2
  
  {"level":"info","time":"Dec 8, 2017 11:32 PM","message":"new active speaker","activePeer":"9f05d96a-9641-4c63-8f0e-486b98e48eb5"}
  
  1512775954773 - stderr: [AVBSFContext @ 0x7f81fc8018e0] nal_unit_type: 7, nal_ref_idc: 3
  
  [AVBSFContext @ 0x7f81fc8018e0] nal_unit_type: 8, nal_ref_idc: 3
  
  [AVBSFContext @ 0x7f81fc8018e0] nal_unit_type: 5, nal_ref_idc: 3
  
  1512775954774 - stderr: [h264 @ 0x7f8200000c00] nal_unit_type: 7, nal_ref_idc: 3
  
  1512775954774 - stderr: [h264 @ 0x7f8200000c00] nal_unit_type: 8, nal_ref_idc: 3
  
  1512775954774 - stderr: [h264 @ 0x7f8200000c00] nal_unit_type: 5, nal_ref_idc: 3
  
  1512775954774 - stderr: [h264 @ 0x7f8200000c00] Reinit context to 640x480, pix_fmt: yuv420p
  
  1512775954801 - stderr: [h264 @ 0x7f8200000c00] nal_unit_type: 1, nal_ref_idc: 3
  
  1512775954939 - stderr: [h264 @ 0x7f8200000c00] nal_unit_type: 7, nal_ref_idc: 3
  
  1512775954939 - stderr: [h264 @ 0x7f8200000c00] nal_unit_type: 8, nal_ref_idc: 3
  
  1512775954940 - stderr: [h264 @ 0x7f8200000c00] nal_unit_type: 5, nal_ref_idc: 3
  
  1512775955003 - stderr: [h264 @ 0x7f8200000c00] nal_unit_type: 1, nal_ref_idc: 3
  
  1512775955999 - stderr:     Last message repeated 3 times
  
  [sdp @ 0x7f81fd000000] All info found
  
  1512775955999 - stderr: [sdp @ 0x7f81fd000000] rfps: 29.750000 0.019566
  
  [sdp @ 0x7f81fd000000] rfps: 29.833333 0.015263
  
  [sdp @ 0x7f81fd000000] rfps: 29.916667 0.011503
  
  1512775955999 - stderr: [sdp @ 0x7f81fd000000] rfps: 30.000000 0.008285
  
  [sdp @ 0x7f81fd000000] rfps: 31.000000 0.011990
  
      Last message repeated 1 times
  
  [sdp @ 0x7f81fd000000] rfps: 29.970030 0.009380
  
  [sdp @ 0x7f81fd000000] After avformat_find_stream_info() pos: 479 bytes read:479 seeks:0 frames:98
  
  1512775956000 - stderr: Input #0, sdp, from 'data:text/plain;base64,dj0wCm89LSAwIDAgSU4gSVA0IDEyNy4wLjAuMQpzPWUwYzkyZmEwLWRhZDUtMTFlNy04Njg3LTA5MGRkYTk1YjFhNCBmb29ib2FyCmM9SU4gSVA0IDEyNy4wLjAuMQptPWF1ZGlvIDIwMDAwIFJUUC9BVlBGIDEwMAphPXNlbmRyZWN2CmE9cnRjcC1tdXgKYT1ydHBtYXA6MTAwIG9wdXMvNDgwMDAvMgphPWZtdHA6MTAwIG1pbnB0aW1lPTEwOyB1c2VpbmJhbmRmZWM9MQptPXZpZGVvIDIwMDAyIFJUUC9BVlBGIDEwMQphPXNlbmRyZWN2CmE9cnRjcC1tdXgKYT1ydHBtYXA6MTAxIEgyNjQvOTAwMDAKYT1ydGNwLWZiOjEwMSBjY20gZmlyCmE9cnRjcC1mYjoxMDEgbmFjawphPXJ0Y3AtZmI6MTAxIG5hY2sgcGxpCmE9cnRjcC1mYjoxMDEgZ29vZy1yZW1iCmE9cnRjcC1mYjoxMDEgdHJhbnNwb3J0LWNjCmE9Zm10cDoxMDEgbGV2ZWwtYXN5bW1ldHJ5LWFsbG93ZWQ9MTtwYWNrZXRpemF0aW9uLW1vZGU9MTtwcm9maWxlLWxldmVsLWlkPTQyZTAxZgo=':
  
  1512775956000 - stderr:   Metadata:
  
      title           : e0c92fa0-dad5-11e7-8687-090dda95b1a4 fooboar
  
    Duration: N/A, start: 0.000000, bitrate: N/A
  
      Stream #0:0, 70, 1/48000: Audio: opus, 48000 Hz, stereo, fltp1512775956000 - stderr:
  
      Stream #0:1, 28, 1/90000: Video: h264 (Constrained Baseline), 1 reference frame, yuv420p(progressive, left), 640x480, 0/1, 30 tbr, 90k tbn, 180k tbc
  
  1512775956000 - stderr: Successfully opened the file.
  
  Parsing a group of options: output url /tmp/archive/e0c92fa0-dad5-11e7-8687-090dda95b1a4_10e1c990-dc70-11e7-888d-9f39ca0c79bc/1512775954465.m3u8.
  
  Applying option vcodec (force video codec ('copy' to copy stream)) with argument copy.
  
  Applying option acodec (force audio codec ('copy' to copy stream)) with argument aac.
  
  Applying option map (set input stream mapping) with argument 0:0,0:1.
  
  Applying option map (set input stream mapping) with argument 0:1,0:1.
  
  Applying option bsf:v (A comma-separated list of bitstream filters) with argument h264_mp4toannexb.
  
  Successfully parsed a group of options.
  
  1512775956000 - stderr: Opening an output file: /tmp/archive/e0c92fa0-dad5-11e7-8687-090dda95b1a4_10e1c990-dc70-11e7-888d-9f39ca0c79bc/1512775954465.m3u8.
  
  1512775956000 - stderr: Successfully opened the file.
  
  1512775956001 - stderr: [AVBSFContext @ 0x7f81fcb020a0] The input looks like it is Annex B already
  
  Stream mapping:
  
  1512775956001 - stderr:   Stream #0:0 -> #0:0 [sync #0:1] (opus (native) -> aac (native))
  
    Stream #0:1 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  cur_dts is invalid (this is harmless if it occurs once at the start per stream)
  
  stream #0:
  
    keyframe=1
  
    duration=0.000
  
    dts=0.000  pts=0.000
  
    size=82
  
  1512775956001 - stderr: [SWR @ 0x7f820001e600] Using fltp internally between filters
  
  1512775956002 - stderr: detected 8 logical cores
  
  1512775956003 - stderr: [graph_0_in_0_0 @ 0x7f81fc90dfc0] Setting 'time_base' to value '1/48000'
  
  [graph_0_in_0_0 @ 0x7f81fc90dfc0] Setting 'sample_rate' to value '48000'
  
  1512775956003 - stderr: [graph_0_in_0_0 @ 0x7f81fc90dfc0] Setting 'sample_fmt' to value 'fltp'
  
  [graph_0_in_0_0 @ 0x7f81fc90dfc0] Setting 'channel_layout' to value '0x3'
  
  [graph_0_in_0_0 @ 0x7f81fc90dfc0] tb:1/48000 samplefmt:fltp samplerate:48000 chlayout:0x3
  
  [format_out_0_0 @ 0x7f81fc914da0] Setting 'sample_fmts' to value 'fltp'
  
  [format_out_0_0 @ 0x7f81fc914da0] Setting 'sample_rates' to value '96000|88200|64000|48000|44100|32000|24000|22050|16000|12000|11025|8000|7350'
  
  1512775956004 - stderr: [AVFilterGraph @ 0x7f81fbd02200] query_formats: 4 queried, 9 merged, 0 already done, 0 delayed
  
  1512775956007 - stderr: [hls @ 0x7f81fd80f000] Opening '/tmp/archive/e0c92fa0-dad5-11e7-8687-090dda95b1a4_10e1c990-dc70-11e7-888d-9f39ca0c79bc/15127759544650.ts' for writing
  
  [file @ 0x7f81fbf01ee0] Setting default whitelist 'file,crypto'
  
  1512775956007 - stderr: [mpegts @ 0x7f81fd877800] muxrate VBR, pcr every 9000 pkts, sdt every 2147483647, pat/pmt every 2147483647 pkts
  
  Output #0, hls, to '/tmp/archive/e0c92fa0-dad5-11e7-8687-090dda95b1a4_10e1c990-dc70-11e7-888d-9f39ca0c79bc/1512775954465.m3u8':
  
    Metadata:
  
      title           : e0c92fa0-dad5-11e7-8687-090dda95b1a4 fooboar
  
      encoder         : Lavf57.83.100
  
  1512775956007 - stderr:     Stream #0:0, 0, 1/90000: Audio: aac (LC), 48000 Hz, stereo, fltp, delay 1024, 128 kb/s
  
      Metadata:
  
        encoder         : Lavc57.107.100 aac
  
      Stream #0:1, 0, 1/90000: Video: h264 (Constrained Baseline), 1 reference frame, yuv420p(progressive, left), 640x480 (0x0), 0/1, q=2-31, 30 tbr, 90k tbn, 90k tbc
  
  cur_dts is invalid (this is harmless if it occurs once at the start per stream)
  
  1512775956007 - stderr:     Last message repeated 1 times
  
  stream #0:
  
    keyframe=1
  
    duration=0.000
  
    dts=0.020  pts=0.020
  
    size=79
  
  1512775956007 - stderr: cur_dts is invalid (this is harmless if it occurs once at the start per stream)
  
      Last message repeated 1 times
  
  stream #0:
  
    keyframe=1
  
    duration=0.000
  
  1512775956007 - stderr:   dts=0.040  pts=0.040
  
    size=75
  
  1512775956014 - stderr: cur_dts is invalid (this is harmless if it occurs once at the start per stream)
  
  stream #0:
  
    keyframe=1
  
    duration=0.000
  
    dts=0.0601512775956014 - stderr:   pts=0.060
  
    size=81
  
  1512775956017 - stderr: cur_dts is invalid (this is harmless if it occurs once at the start per stream)
  
  stream #0:
  
    keyframe=1
  
    duration=0.000
  
    dts=0.080  pts=0.080
  
    size=76
  
  1512775956022 - stderr: cur_dts is invalid (this is harmless if it occurs once at the start per stream)
  
  stream #0:
  
    keyframe=1
  
    duration=0.000
  
    dts=0.1001512775956022 - stderr:   pts=0.100
  
    size=79
  
  1512775956023 - stderr: cur_dts is invalid (this is harmless if it occurs once at the start per stream)
  
  stream #0:
  
    keyframe=1
  
  1512775956023 - stderr:   duration=0.000
  
    dts=0.120  pts=0.120
  
    size=95
  
  1512775956024 - stderr: cur_dts is invalid (this is harmless if it occurs once at the start per stream)
  
  1512775956024 - stderr: stream #0:
  
    keyframe=1
  
    duration=0.000
  
    dts=0.140  pts=0.140
  
    size=93
  
  1512775956025 - stderr: cur_dts is invalid (this is harmless if it occurs once at the start per stream)
  
  stream #0:
  
    keyframe=1
  
  1512775956025 - stderr:   duration=0.000
  
    dts=0.160  pts=0.160
  
    size=94
  
  1512775956026 - stderr: cur_dts is invalid (this is harmless if it occurs once at the start per stream)
  
  stream #1:
  
    keyframe=1
  
  1512775956026 - stderr:   duration=0.000
  
    dts=N/A  pts=N/A
  
    size=992
  
  [hls @ 0x7f81fd80f000] Timestamps are unset in a packet for stream 1. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
  
  1512775956026 - stderr: stream #0:
  
    keyframe=1
  
    duration=0.000
  
  1512775956026 - stderr:   dts=0.180  pts=0.180
  
    size=108
  
  1512775956027 - stderr: stream #1:
  
    keyframe=0
  
    duration=0.000
  
  1512775956027 - stderr:   dts=0.002  pts=0.002
  
    size=3047
  
  [hls @ 0x7f81fd80f000] pkt->duration = 0, maybe the hls segment duration will not precise
  
  stream #0:
  
    keyframe=1
  
    duration=0.000
  
    dts=0.200  pts=0.200
  
    size=89
  
  1512775956060 - stderr: stream #0:
  
    keyframe=1
  
    duration=0.000
  
    dts=0.220  pts=0.220
  
    size=73
  
  stream #0:
  
    keyframe=1
  
    duration=0.000
  
    dts=0.240  pts=0.240
  
    size=78
  
  stream #0:
  
    keyframe=1
  
    duration=0.000
  
    dts=0.260  pts=0.260

  Notice how the first frame for stream #1 (video) starts after a number of audio frames ? Specifically, it starts at stream #0 dts/pts 0.18. In this situation, the a/v sync issue is pretty much unnoticeable, but with a bunch of repros, I’ve determined that the a/v sync offset is always the duration of however long audio frames were sent before the first video frame (sometimes seconds). I’m consistently starting the RTP streams only tens of ms apart, so I can’t control for this variance on the input side.

  After the initial audio frames come in, the first video frame has a dts/pts around 0. What ffmpeg setting would I use to adjust the timestamps accordingly ? I don’t care about losing the starting audio that doesn’t have video, so any solution that would adjust the timestamps works.

• How to Use Web Analytics to Improve SEO

  5 janvier 2022, par erin — Analytics Tips

  Everyone wants their website to rank highly in Google — and that’s exactly why the world of SEO is so competitive.

  In order to succeed in such a crowded space, it’s essential to equip yourself with the right tools and processes to ensure your website is maximally optimised for search engines.

  If you’d like to improve your website’s SEO rankings, leveraging web analytics is one of the best places to start. Web analytics provides valuable insights to help you assess performance, user behaviour and optimisation opportunities.

  In this blog, we’ll cover :

  The basics of SEO and web analytics

  Before we discuss how to use web analytics for SEO, let’s start with a quick explanation of both.

  SEO (Search Engine Optimisation) encompasses a broad set of activities aimed at increasing a website’s position in search engine results pages (SERPs). When a user enters a query (e.g. ‘marketing agencies in Dallas’) in a search engine, the websites that appear near the top of the page are optimised for search engines and therefore ranking for that particular term. 

  Web analytics refers to the monitoring/assessment of metrics that track traffic sources and user behaviour on a website. This involves the use of a web analytics tool to collect, aggregate, organise and visualise website data so that meaningful conclusions can be drawn.

  The importance of website analytics for SEO

  SEO revolves around search engine algorithms – a set of rules that dictates a website’s ranking for a given search query (i.e. keyword). The algorithm takes numerous factors into account to determine a particular site’s SERP ranking. So, to achieve strong SEO, your website needs to exhibit qualities that the algorithm deems important. That’s where web analytics comes into play.

  Web analytics allows you to track key metrics and data points that affect how the algorithm ranks your website. For example, how much time do users spend on your site ? Which external links are referring traffic to your site ? How do your site’s Core Web Vitals stack up ? 

  Understanding this data will supply you with the insights needed to make positive adjustments, ultimately improving your website’s SEO. 

  How do you analyse a website for SEO ?

  The SEO analysis of a website needs to be focused on relevant data that’s applicable to search engine rankings. When conducting your website SEO analysis, here are some notable metrics and data fields to pay attention to :

  1. Bounce rate and dwell time

  These metrics denote how much time users spend on your website. If users frequently exit your site after only a few seconds, Google may view this as a negative indicator. To reduce bounce rate and increase dwell time, you should work towards making your site’s content more captivating and ensuring that there aren’t any technical issues with your site (e.g. pages taking too long to load or not optimised for mobile).

  

  2. Broken/dead links

  Perform a technical analysis to scan your website for faulty links. If your site contains broken links that lead to 404 pages, this can detract from your website’s SEO rankings. Redirect those links to a related page or remove them.

  

  Matomo’s Crawling Errors report can give you instant access to this technical information so you can resolve it before it begins to impact your ranking.

  3. Scroll depth

  Measuring scroll depth (how far users scroll down the page) can help you gauge the quality of your content — and this goes hand-in-hand with bounce rate and dwell time. To assess scroll depth, you can use a Tag Manager to track the specific scroll percentage on your site’s pages.

  4. Transitions

  Studying how users transition from page to page within your site can help you understand their behaviour more holistically. Which pages do they tend to gravitate towards ? Are there CTAs on your blog that aren’t driving many click-throughs ? Optimising user journeys will, in turn, elevate the overall user experience on your site.

  

  5. Internal site search

  You can use site search tracking and reporting to learn what your audience is looking for. If you notice a trend (e.g. the majority of searches are for pricing because your pricing page isn’t in the navigation menu), this can inform both site architecture and content planning.

  

  Ecommerce sites in particular should be monitoring branded queries, especially in regards to brand misspellings that could be causing users to bounce off the site.

  6. Segments

  Separating your visitors into distinct segments can produce granular insights that paint a more accurate picture.

  For example, perhaps you notice that your bounce rate is far higher on mobile, or with users from the UK. In both cases, this knowledge will provide clarity on where to focus your optimisation efforts (e.g. mobile responsiveness, UK-specific content/landing pages, etc.).

  

  7. Acquisition channels

  It’s crucial to analyse where your website traffic is coming from. Among other things, reviewing your acquisition metrics will reveal which external websites are referring the most traffic to your website. 

  Links from external sites (also known as backlinks) are one of the most important ranking factors because this tells Google that your site is reputable and credible. So, you may choose to cultivate a relationship with these sites (or similar sites) by offering guest blogging and other link building initiatives.

  

  In addition to the above, you should also be monitoring your Core Web Vitals — which leads us to our next section.

  What are Core Web Vitals and why are they important ?

  Core Web Vitals are a set of 3 primary metrics that reflect the general user experience of a website. These metrics are load time, interactivity and stability. 

  1. Load time (LCP) refers to the amount of time it takes for your website’s text and images to load.
  2. Interactivity (FID) refers to the amount of time it takes for user input areas (buttons, form fields, etc.) to become functional.
  3. Stability (CLS) refers to the visual/spatial integrity of your website. If text, images, and other elements tend to suddenly shift position when a user is viewing the site, this will hurt your CLS score.

  

  So, why are these Core Web Vitals metrics important for SEO ? Generally speaking, Google prioritises user experience — and Core Web Vitals affect users’ satisfaction with a website. Furthermore, Google has confirmed that Core Web Vitals are, indeed, a ranking factor.

  Matomo enables you to track metrics for Core Web Vitals which we refer to as SEO Web Vitals.

  How to measure and track keyword performance

  We can’t talk about SEO and analytics without touching on keywords. Keywords (the words/phrases that users type in a search engine) are arguably the most cardinal component of SEO. So, outside of website performance, it’s also necessary to track the keywords your website is ranking for. 

  Recall from above that SEO is all about ranking highly on SERPs for certain search queries (i.e. keywords). To assess your Search Engine Keyword Performance, you can use an analytics tool to view Keyword reports for your website. These reports will show you which keywords your site ranks for, the average SERP position your site achieves for each keyword, the amount of traffic you receive from each keyword, and more.

  

  Digging into your keyword performance can help you identify valuable keyword opportunities and improvement goals.

  For example, upon reviewing your highest-traffic keywords, you may choose to create more blog content around those keywords to bolster your success. Or, perhaps you notice that your average position for a high-intent keyword is quite low. In that case, you could implement a targeted link building campaign to help boost your ranking for that keyword. 

  Final thoughts

  In this article, we’ve discussed the benefits of web analytics — particularly in regards to SEO. When it comes to selecting a web analytics tool, Google Analytics is by far the most popular choice. But that doesn’t make it the best.

  At Matomo, we’re committed to providing a superior alternative to Google Analytics. Matomo is a powerful, open-source web analytics platform that gives you 100% data ownership — protecting both your data and your customers’ privacy.

  Try our live demo or start a free 21-day trial now – no credit card required.

• Matomo’s 2021 Year in Review

  13 décembre 2021, par erin — Community

  2021 has been an exciting year at Matomo !

  We’re grateful for all community members who reported feedback and suggestions, our awesome team of translators for their work, and our Premium features customers and Matomo Cloud hosting customers for their amazing support. 

  We wanted to share some quick highlights to remind you of the exciting things that happened in 2021.

  Matomo continues to develop

  In 2021 we released a number of new features including :

  • SEO Web Vitals

  The new SEO Web Vitals feature helps you track your critical website performance metrics, which are a core element of SEO best practice.

  

  • Advertising Conversion Export 

  Measure the performance of your ads without giving up privacy.

  This exciting new feature supports privacy and compliance requirements by eliminating the need to put third-party advertising tracking codes on your site. Now marketers can easily import conversion data from Matomo into Google Ads, Microsoft Advertising or Yandex Ads.

  • Tracking Spam Prevention 

  Say goodbye to spammers & bots making your data inaccurate and say hello to reliable data. 

  This powerful plugin provides our self-hosting users various options to prevent spammers and bots from making data inaccurate so you can rely on your data again.

  • In 2021 we moved from Matomo 4.1.0 to Matomo 4.6.0, with our new releases delivering over 600 updates to improve the stability and functionality of the product.

  Some of our team’s favourite updates in 2021 included :

  • • Graphs now show a difference for data of “unfinished” and “complete” periods, with unfinished periods now indicated by a dashed line.
    • Improvements to Matomo Tag Manager’s debugger – now you can simply enter the URL in a form and click Debug.
    • Dashboards now show proportional evolution comparison for incomplete periods (rather than absolute values).
     
  • We also rolled out general bug fixes in Matomo Mobile 2.5 for iOS and Android.
  • Continuous improvements to Matomo for WordPress. 

  In other news

  • Au revoir, tracking consent. France’s data protection authority, Commission nationale de l’informatique et des libertés (CNIL), announced that Matomo is now exempt from tracking consent in France (under conditions).
  • We lowered the pricing for Matomo Cloud, the starting price is now 19 EUR or 19 USD per month.
  • For our self-hosting users, we introduced a 30-day Free Trial for Marketplace Premium Plugins. 

  If you haven’t explored our Marketplace yet, some of our most popular plugins include :

  • • Form Analytics
    • Search Engine Keyword Performance
    • Heatmaps and Session Recordings
     
  • Out of a substantial list of 320 products, Matomo was recognised by Capterra as a leading global Web Analytics Software solution for 2021.

  Matomo Community working together

  MatomoCamp 2021 was a massive success thanks to our passionate community, sponsors and speakers. This virtual event was run by the Matomo Community, for the Matomo Community. 

  

  Some of the most popular sessions included :

  • How to stay compliant with privacy regulations with Matomo 
  • Use Matomo properly for SEO (German)
  • How does risk for a DPO differ from classical risk perceptions ?
  • Are we there yet ? The present & future of surveillance societies
  • How to manage a Matomo with millions of pageviews per month ?

  All MatomoCamp sessions are now available on-demand. Enjoy !

  More people are choosing ethical analytics 

  We surpassed the incredible milestone of 30K active Matomo for WordPress installations.

  How can you get involved in 2022 ?

  Our mission at Matomo is :

  “To create, as a community, the leading open digital analytics platform, that gives every user full control of their data”

  Join our mission by writing about Matomo on your blog, website, Twitter, talk at conferences or let your friends and colleagues know what is Matomo. 

  Use the Matomo forum if you have any questions or feedback (free support), or purchase a Support Plan to get professional support and guidance.

  To improve Matomo in your language, consider contributing to translations.

  You can also support our efforts by purchasing Premium Features for Matomo or try our Matomo Cloud solution.

  Thank you for being part of our Matomo community, we wish you all the best for 2022 !