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• How to seek mp4 aac audio using Media Source Extensions

  29 août 2018, par Chris

  Please can someone offer me a few pointers when trying to seek within streamed aac audio in mp4 containers ? I’m trying to develop a music download service that sips data via ranged requests rather than simply link to a mp4 file as an <audio></audio> src. (which will instead buffer the whole file as quickly as possible, and so be rather wasteful and expensive).

  So far I’ve managed to successfully append sequential audio range buffers to the SourceBuffer object using partial/ranged requests, attached to my suitably mime-typed MediaSource object. But as soon as I try to seek, the wheels come off and I receive a ’CHUNK_DEMUXER_ERROR_APPEND_FAILED’ error, with the specific issue : ’stream parsing failed’.

  I’ve prepared my mp4 files by encoding them with ffmpeg (via the fluent ffmpeg module), rewriting the movie header box at the start of the file (via the -movflags faststart setting) so that the duration can be parsed. I then fragment the file with mp4fragment (part of the Bento4 tools) with the default settings, and check to ensure the structure of the file matches the format specified by ISO BMFF, with pairs of movie fragments and data boxes (moof/mdat) describing the audio stream. Given the source buffer has no problem playing from the beginning, with contiguous subsequent ranges, this appears to confirm that the format of the mp4 file is acceptable.

  As an aside, I’ve tried fragmenting the file completely in ffmpeg/fluent ffmpeg (using the ’-movflags empty_moov+default_base_moof’ options), but while this works, it also removes the duration from the moov as you’d expect, so the file gets larger during playback as more fragments are fetched and appended. If I set the file duration manually, I still have the issue of not being able to seek to unbuffered audio, so I only seem to be making life more difficult trying to fragment the file solely in ffmpeg.

  So how should I go about seeking within the stream ? I gather that seeking effectively ’needle-drops’ randomly, and so the source buffer might struggle to parse the data out of context, but I imagined that it would skip to the next available fragment in the range that I fetch (which is calculated using the percentage of the seek bar width to set the player.currentTime, which is then converted to a suitable byte range using the 128kbps CBR figure to convert seconds to bytes, to send a 206 partial range request).

  I’ve seen mention of buffer offsets, but I don’t understand how these apply. Most of the dev examples I’ve seen just focus on whole files or segmented videos, rather than fragmented single audio files for seeking ? Do I need to somehow retain a portion of the data from the moov box when seeking for the source buffer to be able to parse it ? In the trun box I have a data offset that varies between two values throughout the file, 444 and 448, depending on whether the sample count is 86 or 87. I’m not sure why it’s not consistent.

  Here’s what the moov looks like from my audio file :

  [ftyp] size=8+24
  
    major_brand = isom
  
    minor_version = 200
  
    compatible_brand = isom
  
    compatible_brand = iso2
  
    compatible_brand = mp41
  
    compatible_brand = iso5
  
  [moov] size=8+620
  
    [mvhd] size=12+96
  
      timescale = 1000
  
      duration = 350047
  
      duration(ms) = 350047
  
    [trak] size=8+448
  
      [tkhd] size=12+80, flags=7
  
        enabled = 1
  
        id = 1
  
        duration = 350047
  
        width = 0.000000
  
        height = 0.000000
  
      [edts] size=8+28
  
        [elst] size=12+16
  
          entry count = 1
  
          entry/segment duration = 350000
  
          entry/media time = 2048
  
          entry/media rate = 1
  
      [mdia] size=8+312
  
        [mdhd] size=12+20
  
          timescale = 44100
  
          duration = 0
  
          duration(ms) = 0
  
          language = und
  
        [hdlr] size=12+41
  
          handler_type = soun
  
          handler_name = Bento4 Sound Handler
  
        [minf] size=8+219
  
          [smhd] size=12+4
  
            balance = 0
  
          [dinf] size=8+28
  
            [dref] size=12+16
  
              [url ] size=12+0, flags=1
  
                location = [local to file]
  
          [stbl] size=8+159
  
            [stsd] size=12+79
  
              entry-count = 1
  
              [mp4a] size=8+67
  
                data_reference_index = 1
  
                channel_count = 2
  
                sample_size = 16
  
                sample_rate = 44100
  
                [esds] size=12+27
  
                  [ESDescriptor] size=2+25
  
                    es_id = 0
  
                    stream_priority = 0
  
                    [DecoderConfig] size=2+17
  
                      stream_type = 5
  
                      object_type = 64
  
                      up_stream = 0
  
                      buffer_size = 0
  
                      max_bitrate = 128006
  
                      avg_bitrate = 128006
  
                      DecoderSpecificInfo = 12 10 
  
                    [Descriptor:06] size=2+1
  
            [stts] size=12+4
  
              entry_count = 0
  
            [stsc] size=12+4
  
              entry_count = 0
  
            [stsz] size=12+8
  
              sample_size = 0
  
              sample_count = 0
  
            [stco] size=12+4
  
              entry_count = 0
  
    [mvex] size=8+48
  
      [mehd] size=12+4
  
        duration = 350047
  
      [trex] size=12+20
  
        track id = 1
  
        default sample description index = 1
  
        default sample duration = 0
  
        default sample size = 0
  
        default sample flags = 0

  And here’s a typical fragment :

  [moof] size=8+428
  
    [mfhd] size=12+4
  
      sequence number = 1
  
    [traf] size=8+404
  
      [tfhd] size=12+8, flags=20008
  
        track ID = 1
  
        default sample duration = 1024
  
      [tfdt] size=12+8, version=1
  
        base media decode time = 0
  
      [trun] size=12+352, flags=201
  
        sample count = 86
  
        data offset = 444
  
  [mdat] size=8+32653

  Does that all look good ? Any pointers for seeking within such a file would be hugely appreciated. Thanks !

• Running Windows XP In 2016

  2 janvier 2016, par Multimedia Mike

  I have an interest in getting a 32-bit Windows XP machine up and running. I have a really good yet slightly dated and discarded computer that seemed like a good candidate for dedicating to this task. So the question is : Can Windows XP still be installed from scratch on a computer, activated, and used in 2016 ? I wasn’t quite sure since I have heard stories about how Microsoft has formally ended support for Windows XP as of the first half of 2014 and I wasn’t entirely sure what that meant.

  Spoiler : It’s still possible to install and activate Windows XP as of the writing of this post. It’s also possible to download and install all the updates published up until support ended.

  The Candidate Computer
  This computer was assembled either in late 2008 or early 2009. It was a beast at the time.

  
  
  Click for a larger image
  

  It was built around the newly-released NVIDIA GTX 280 video card. The case is a Thermaltake DH-101, which is a home theater PC thing. The motherboard is an Asus P5N32-SLI Premium with a Core 2 Duo X6800 2.93 GHz CPU on board. 2 GB of RAM and a 1.5 TB hard drive are also present.

  The original owner handed it off to me because their family didn’t have much use for it anymore (too many other machines in the house). Plus it was really, obnoxiously loud. The noisy culprit was the stock blue fan that came packaged with the Intel processor (seen in the photo) whining at around 65 dB. I replaced the fan and brought the noise level way down.

  As for connectivity, the motherboard has dual gigabit NICs (of 2 different chipsets for some reason) and onboard wireless 802.11g. I couldn’t make the latter work and this project was taking place a significant distance from my wired network. Instead, I connected a USB 802.11ac dongle and antenna which is advertised to work in both Windows XP and Linux. It works great under Windows XP. Meanwhile, making the adapter work under Linux provided a retro-computing adventure in which I had to modify C code to make the driver work.

  So, score 1 for Windows XP over Linux here.

  The Simple Joy of Retro-computing
  One thing you have to watch out for when you get into retro-computing is fighting the urge to rant about the good old days of computing. Most long-time computer users have a good understanding of the frustration that computers keep getting faster by orders of magnitude and yet using them somehow feels slower and slower over successive software generations.
  

  This really hits home when you get old software running, especially on high-end hardware (relative to what was standard contemporary hardware). After I got this new Windows XP machine running, as usual, I was left wondering why software was so much faster a few generations ago.

  Of course, as mentioned, it helps when you get to run old software on hardware that would have been unthinkably high end at the software’s release. Apparently, the minimum WinXP specs as set by MS are a 233 MHz Pentium CPU and 64 MB of RAM, with 1.5 GB of hard drive space. This machine has more than 10x the clock speed (and 2 CPUs), 32x the RAM, and 1000x the HD space. Further, I’m pretty sure 100 Mbit ethernet was the standard consumer gear in 2001 while 802.11b wireless was gaining traction. The 802.11ac adapter makes networking quite pleasant.

  Purpose
  Retro-computing really seems to be ramping up in popularity lately. For some reason, I feel compelled to declare at this juncture that I was into it before it was cool.

  Why am I doing this ? I have a huge collection of old DOS/Windows computer games. I also have this nerdy obsession with documenting old video games in the MobyGames database. I used to do a lot of this a few years ago, tracking the effort on my gaming blog. In the intervening years, I have still collected a lot of old, unused, unloved video games, usually either free or very cheap while documenting my collection efforts on that same blog.

  So I want to work my way through some of this backlog, particularly the games that are not yet represented in the MobyGames database, and even more pressing, ones that the internet (viewed through Google at least) does not seem to know about. To that end, I thought this was a good excuse to get Windows XP on this old machine. A 32-bit Windows XP machine is capable of running any software advertised as supporting Windows XP, Windows ME, Windows 98, Windows 95, and even 16-bit Windows 3.x (I have games for all these systems). That covers a significant chunk of PC history. It can probably be made to run DOS games as well, but those are (usually) better run under DosBox. In order to get the right display feel, I even invested in a (used) monitor sporting a 4:3 aspect ratio. If I know these old games, most will be engineered and optimized for that ratio rather than the widescreen resolutions seen nowadays.

  I would also like to get back to that Xbox optical disc experimentation I was working on a few years ago. Another nice feature of this motherboard is that it still provides a 40-pin IDE/PATA adapter which makes the machine useful for continuing that old investigation (and explains why I have that long IDE cable to no where pictured hanging off the board).

  The Messy Details
  I did the entire installation process twice. The first time was a bumbling journey of discovery and copious note-taking. I still have Windows XP installation media that includes service pack 2 (SP2), along with 2 separate licenses that haven’t been activated for a long time. My plan was to install it fresh, then install the relevant drivers. Then I would investigate the Windows update and activation issues and everything should be fine.

  So what’s the deal with Windows Update for XP, and with activations ? Second item first : it IS possible to still activate Windows XP. The servers are still alive and respond quickly. However, as always, you don’t activate until you’re sure everything is working at some baseline. It took awhile to get there.

  As for whether Windows Update still works for XP, that’s a tougher question. Short answer is yes ; longer answer is that it can be difficult to kick off the update process. At least on SP2, the “Windows Update” program launches IE6 and navigates to a special microsoft.com URL which initiates the update process (starting with an ActiveX control). This URL no longer exists.

  From what I can piece together from my notes, this seems to be the route I eventually took :

  1. Install Windows XP fresh
  2. Install drivers for the hardware ; fortunately, Asus still has all the latest drivers necessary for the motherboard and its components but it’s necessary to download these from another network-connected PC since the networking probably won’t be running “out of the box”
  3. Download the .NET 3.5 runtime, which is the last one supported by Windows XP, and install it
  4. Download the latest NVIDIA drivers ; this needs to be done after the previous step because the installer requires the .NET runtime ; run the driver installer and don’t try to understand why it insists on re-downloading .NET 3.5 runtime before installation
  5. While you’re downloading stuff on other computers to be transported to this new machine, be sure to download either Chrome or Firefox per your preference ; if you try to download via IE6, you may find that their download pages aren’t compatible with IE6
  6. Somewhere along the line (I’m guessing as a side effect of the .NET 3.5 installation), the proper, non-IE6-based Windows Update program magically springs to life ; once this happens, there will be 144 updates (in my case anyway) ; installing these will probably require multiple reboots, but SP3 and all known pre-deprecation security fixes will be installed
  7. Expect that, even after installing all of these, a few more updates will appear ; eventually, you’ll be at the end of the update road
  8. Once you’re satisfied everything is working satisfactorily, take the plunge and activate your installation

  Residual Quirks
  Steam runs great on Windows XP, as do numerous games I have purchased through the service. So that opens up a whole bunch more games that I could play on this machine. Steam’s installer highlights a curious legacy problem of Windows XP– it seems there are many languages that it does not support “out of the box” :

  
  
  

  It looks like the Chinese options and a few others that are standard now weren’t standard 15 years ago.

  Also, a little while after booting up, I’ll get a crashing error concerning a process called geoforms.scr. This appears to be NVIDIA-related. However, I don’t notice anything obviously operationally wrong with the system.

  Regarding DirectX support, DirectX 9 is the highest version officially supported by Windows XP. There are allegedly methods to get DirectX 10 running as well, but I don’t care that much. I did care, briefly, when I realized that a bunch of the demos for the NVIDIA GTX 280 required DX10 which left me wondering why it was possible to install them on Windows XP.

  Eventually, by installing enough of these old games, I fully expect to have numerous versions of .NET, DirectX, QT, and Video for Windows installed side by side.

  Out of curiosity, I tried playing a YouTube HD/1080p video. I wanted to see if the video was accelerated through my card. The video played at full speed but I noticed some tearing. Then I inspected the CPU usage and noticed that the CPU was quite loaded. So either the GTX 280 doesn’t have video acceleration, or Windows XP doesn’t provide the right APIs, or Chrome is not able to access the APIs in Windows XP, or perhaps some combination of the foregoing.

  Games are working well, though. I tried one of my favorite casual games and got sucked into that for, like, an entire night because that’s what casual games do. But then, I booted up a copy of WarCraft III that I procured sometime ago. I don’t have any experience with the WarCraft universe (RTS or MMO) but I developed a keen interest in StarCraft II over the past few years and wanted to try WarCraft III. Unfortunately, I couldn’t get WarCraft III to work correctly on several different Windows 7 installations (movies didn’t play, which left me slightly confused as to what I was supposed to do).

  Still works beautifully on the new old Windows XP machine.

• Is Google Analytics Accurate ? 6 Important Caveats

  8 novembre 2022, par Erin

  It’s no secret that accurate website analytics is crucial for growing your online business — and Google Analytics is often the go-to source for insights. 

  But is Google Analytics data accurate ? Can you fully trust the provided numbers ? Here’s a detailed explainer.

  How Accurate is Google Analytics ? A Data-Backed Answer 

  When properly configured, Google Analytics (Universal Analytics and Google Analytics 4) is moderately accurate for global traffic collection. That said : Google Analytics doesn’t accurately report European traffic. 

  According to GDPR provisions, sites using GA products must display a cookie consent banner. This consent is required to collect third-party cookies — a tracking mechanism for identifying users across web properties.

  Google Analytics (GA) cannot process data about the user’s visit if they rejected cookies. In such cases, your analytics reports will be incomplete.

  Cookie rejection refers to visitors declining or blocking cookies from ever being collected by a specific website (or within their browser). It immediately affects the accuracy of all metrics in Google Analytics.

  Google Analytics is not accurate in locations where cookie consent to tracking is legally required. Most consumers don’t like disruptive cookie banners or harbour concerns about their privacy — and chose to reject tracking. 

  This leaves businesses with incomplete data, which, in turn, results in : 

  • Lower traffic counts as you’re not collecting 100% of the visitor data. 
  • Loss of website optimisation capabilities. You can’t make data-backed decisions due to inconsistent reporting

  For the above reasons, many companies now consider cookieless website tracking apps that don’t require consent screen displays. 

  Why is Google Analytics Not Accurate ? 6 Causes and Solutions 

  A high rejection rate of cookie banners is the main reason for inaccurate Google Analytics reporting. In addition, your account settings can also hinder Google Analytics’ accuracy.

  If your analytics data looks wonky, check for these six Google Analytics accuracy problems. 

  You Need to Secure Consent to Cookies Collection 

  To be GDPR-compliant, you must display a cookie consent screen to all European users. Likewise, other jurisdictions and industries require similar measures for user data collection. 

  This is a nuisance for many businesses since cookie rejection undermines their remarketing capabilities. Hence, some try to maximise cookie acceptance rates with dark patterns. For example : hide the option to decline tracking or make the texts too small. 

  

  Sadly, not everyone’s treating users with respect. A joint study by German and American researchers found that only 11% of US websites (from a sample of 5,000+) use GDPR-compliant cookie banners.

  As a result, many users aren’t aware of the background data collection to which they have (or have not) given consent. Another analysis of 200,000 cookies discovered that 70% of third-party marketing cookies transfer user data outside of the EU — a practice in breach of GDPR.

  Naturally, data regulators and activities are after this issue. In April 2022, Google was pressured to introduce a ‘reject all’ cookies button to all of its products (a €150 million compliance fine likely helped with that). Whereas, noyb has lodged over 220 complaints against individual websites with deceptive cookie consent banners.

  The takeaway ? Messing up with the cookie consent mechanism can get you in legal trouble. Don’t use sneaky banners as there are better ways to collect website traffic statistics. 

  Solution : Try Matomo GDPR-Friendly Analytics 

  Fill in the gaps in your traffic analytics with Matomo – a fully GDPR-compliant product that doesn’t rely on third-party cookies for tracking web visitors. Because of how it is designed, the French data protection authority (CNIL) confirmed that Matomo can be used to collect data without tracking consent.

  With Matomo, you can track website users without asking for cookie consent. And when you do, we supply you with a compact, compliant, non-disruptive cookie banner design. 

  Your Google Tag Isn’t Embedded Correctly 

  Google Tag (gtag.js) is a web tracking script that sends data to your Google Analytics, Google Ads and Google Marketing Platform.

  A corrupted gtag.js installation can create two accuracy issues : 

  • Duplicate page tracking 
  • Missing script installation 

  Is there a way to tell if you’re affected ?

  Yes. You may have duplicate scripts installed if you have a very low bounce rate on most website pages (below 15% – 20%). The above can happen if you’re using a WordPress GA plugin and additionally embed gtag.js straight in your website code. 

  A tell-tale sign of a missing script on some pages is low/no traffic stats. Google alerts you about this with a banner : 

  

  Solution : Use Available Troubleshooting Tools 

  Use Google Analytics Debugger extension to analyse pages with low bounce rates. Use the search bar to locate duplicate code-tracking elements. 

  Alternatively, you can use Google Tag Assistant for diagnosing snippet install and troubleshooting issues on individual pages. 

  If the above didn’t work, re-install your analytics script. 

  Machine Learning and Blended Data Are Applied

  Google Analytics 4 (GA4) relies a lot on machine learning and algorithmic predictions.

  By applying Google’s advanced machine learning models, the new Analytics can automatically alert you to significant trends in your data. [...] For example, it calculates churn probability so you can more efficiently invest in retaining customers.

  Vidhya Srinivasan, VP of Measurement, Analytics and Buying Platforms at Google

  On the surface, the above sounds exciting. In practice, Google’s application of predictive algorithms means you’re not seeing actual data. 

  To offer a variation of cookieless tracking, Google algorithms close the gaps in reporting by creating models (i.e., data-backed predictions) instead of reporting on actual user behaviours. Therefore, your GA4 numbers may not be accurate.

  For bigger web properties (think websites with 1+ million users), Google also relies on data sampling — a practice of extrapolating data analytics, based on a data subset, rather than the entire dataset. Once again, this can lead to inconsistencies in reporting with some numbers (e.g., average conversion rates) being inflated or downplayed. 

  Solution : Try an Alternative Website Analytics App 

  Unlike GA4, Matomo reports consist of 100% unsampled data. All the aggregated reporting you see is based on real user data (not guesstimation). 

  Moreover, you can migrate from Universal Analytics (UA) to Matomo without losing access to your historical records. GA4 doesn’t yet have any backward compatibility.

  Spam and Bot Traffic Isn’t Filtered Out 

  Surprise ! 42% of all Internet traffic is generated by bots, of which 27.7% are bad ones.

  Good bots (aka crawlers) do essential web “housekeeping” tasks like indexing web pages. Bad bots distribute malware, spam contact forms, hack user accounts and do other nasty stuff. 

  A lot of such spam bots are designed specifically for web analytics apps. The goal ? Flood your dashboard with bogus data in hopes of getting some return action from your side. 

  Types of Google Analytics Spam :

  • Referral spam. Spambots hijack the referrer, displayed in your GA referral traffic report to indicate a page visit from some random website (which didn’t actually occur). 
  • Event spam. Bots generate fake events with free language entries enticing you to visit their website. 
  • Ghost traffic spam. Malicious parties can also inject fake pageviews, containing URLs that they want you to click. 

  Obviously, such spammy entities distort the real website analytics numbers. 

  Solution : Set Up Bot/Spam Filters 

  Google Analytics 4 has automatic filtering of bot traffic enabled for all tracked Web and App properties. 

  But if you’re using Universal Analytics, you’ll have to manually configure spam filtering. First, create a new view and then set up a custom filter. Program it to exclude :

  • Filter Field : Request URI
  • Filter Pattern : Bot traffic URL

  Once you’ve configured everything, validate the results using Verify this filter feature. Then repeat the process for other fishy URLs, hostnames and IP addresses. 

  You Don’t Filter Internal Traffic 

  Your team(s) spend a lot of time on your website — and their sporadic behaviours can impair your traffic counts and other website metrics.

  To keep your data “employee-free”, exclude traffic from : 

  • Your corporate IPs addresses 
  • Known personal IPs of employees (for remote workers) 

  If you also have a separate stage version of your website, you should also filter out all traffic coming from it. Your developers, contractors and marketing people spend a lot of time fiddling with your website. This can cause a big discrepancy in average time on page and engagement rates. 

  Solution : Set Internal Traffic Filters 

  Google provides instructions for excluding internal traffic from your reports using IPv4/IPv6 address filters. 

  

  Session Timeouts After 30 Minutes 

  After 30 minutes of inactivity, Google Analytics tracking sessions start over. Inactivity means no recorded interaction hits during this time. 

  Session timeouts can be a problem for some websites as users often pin a tab to check it back later. Because of this, you can count the same user twice or more — and this leads to skewed reporting. 

  Solution : Programme Custom Timeout Sessions

  You can codify custom cookie timeout sessions with the following code snippets : 

  • _setSessionCookieTimeout. Set a custom new session cookie timeout in milliseconds.
  • _setVisitorCookieTimeout. Sets a custom Google Analytics visitor cookie expiration time frame in milliseconds.

  Final Thoughts 

  Thanks to its scale and longevity, Google Analytics has some strong sides, but its data accuracy isn’t 100% perfect.

  The inability to capture analytics data from users who don’t consent to cookie tracking and data sampling applied to bigger web properties may be a deal-breaker for your business. 

  If that’s the case, try Matomo — a GDPR-compliant, accurate web analytics solution. Start your 21-day free trial now. No credit card required.

  21 day free trial. No credit card required.

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