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  • MediaSPIP v0.2

    21 juin 2013, par

    MediaSPIP 0.2 est la première version de MediaSPIP stable.
    Sa date de sortie officielle est le 21 juin 2013 et est annoncée ici.
    Le fichier zip ici présent contient uniquement les sources de MediaSPIP en version standalone.
    Comme pour la version précédente, il est nécessaire d’installer manuellement l’ensemble des dépendances logicielles sur le serveur.
    Si vous souhaitez utiliser cette archive pour une installation en mode ferme, il vous faudra également procéder à d’autres modifications (...)

  • Les tâches Cron régulières de la ferme

    1er décembre 2010, par

    La gestion de la ferme passe par l’exécution à intervalle régulier de plusieurs tâches répétitives dites Cron.
    Le super Cron (gestion_mutu_super_cron)
    Cette tâche, planifiée chaque minute, a pour simple effet d’appeler le Cron de l’ensemble des instances de la mutualisation régulièrement. Couplée avec un Cron système sur le site central de la mutualisation, cela permet de simplement générer des visites régulières sur les différents sites et éviter que les tâches des sites peu visités soient trop (...)

  • Mise à disposition des fichiers

    14 avril 2011, par

    Par défaut, lors de son initialisation, MediaSPIP ne permet pas aux visiteurs de télécharger les fichiers qu’ils soient originaux ou le résultat de leur transformation ou encodage. Il permet uniquement de les visualiser.
    Cependant, il est possible et facile d’autoriser les visiteurs à avoir accès à ces documents et ce sous différentes formes.
    Tout cela se passe dans la page de configuration du squelette. Il vous faut aller dans l’espace d’administration du canal, et choisir dans la navigation (...)

Sur d’autres sites (5754)

  • 5 Top Google Optimize Alternatives to Consider

    17 mars 2023, par Erin — Analytics Tips

    Google Optimize is a popular conversion rate optimization (CRO) tool from Alphabet (parent company of Google). With it, you can run A/B, multivariate, and redirect tests to figure out which web page designs perform best. 

    Google Optimize seamlessly integrates with Google Analytics (GA). It also has a free tier. So many marketers chose it as their default A/B testing tool…until recently. 

    Google will sunset Google Optimize by 30 September 2023

    Starting from this date, Google will no longer support Optimize and Optimize 360 (premium edition). All experiments, active after this date, will be paused automatically and you’ll no longer have access to your historical records (unless these are exported in advance).

    The better news is that you still have time to find a Google Optimize alternative — and this post will help you with that. 

    Disclaimer : Please note that the information provided in this blog post is for general informational purposes only and is not intended to provide legal advice. Every situation is unique and requires a specific legal analysis. If you have any questions regarding the legal implications of any matter, please consult with your legal team or seek advice from a qualified legal professional. 

    Best Google Optimize Alternatives 

    Google Optimize was among the first free A/B testing apps. But as with any product, it has some disadvantages. 

    Data updates happen every 24 hours, not in real-time. A free account has caps on the number of experiments. You cannot run more than 5 experiments at a time or implement over 16 combinations for multivariate testing (MVT). A premium version (Optimize 365) has fewer usage constraints, but it costs north of $150K per year. 

    Google Optimize has native integration with GA (of course), so you can review all the CRO data without switching apps. But Optimize doesn’t work well with Google Analytics alternatives, which many choose to use for privacy-friendly user tracking, higher data accuracy and GDPR compliance. 

    At the same time, many other conversion rate optimization (CRO) tools have emerged, often boasting better accuracy and more competitive features than Google Optimize.

    Here are 5 alternative A/B testing apps worth considering.

    Adobe Target 

    Adobe Target Homepage

    Adobe Target is an advanced personalization platform for optimising user and marketing experiences on digital properties. It uses machine learning algorithms to deliver dynamic content, personalised promotions and custom browsing experiences to visitors based on their behaviour and demographic data. 

    Adobe Target also provides A/B testing and multivariate testing (MVT) capabilities to help marketers test and refine their digital experiences.

    Key features : 

    • Visual experience builder for A/B tests setup and replication 
    • Full factorial multivariate tests and multi-armed bandit testing
    • Omnichannel personalisation across web properties 
    • Multiple audience segmentation and targeting options 
    • Personalised content, media and product recommendations 
    • Advanced customer intelligence (in conjunction with other Adobe products)

    Pros

    • Convenient A/B test design tool 
    • Acucate MVT and MAB results 
    • Powerful segmentation capabilities 
    • Access to extra behavioural analytics 
    • One-click personalisation activation 
    • Supports rules-based, location-based and contextual personalisation
    • Robust omnichannel analytics in conjunction with other Adobe products 

    Cons 

    • Requires an Adobe Marketing Cloud subscription 
    • No free trial or freemium tier 
    • More complex product setup and configuration 
    • Steep learning curve for new users 

    Price : On-demand. 

    Adobe Target is sold as part of Adobe Marketing Cloud. Licence costs vary, based on selected subscriptions and the number of users, but are typically above $10K.

    Google Optimize vs Adobe Target : The Verdict 

    Google Optimize comes with a free tier, unlike Adobe Target. It provides you with a basic builder for A/B and MVT tests, but none of the personalisation tools Adobe has. Because of ease-of-use and low price, other Google Optimize alternatives are better suited for small to medium-sized businesses, doing baseline CRO for funnel optimisation. 

    Adobe Target pulls you into the vast Adobe marketing ecosystem, offering omnipotent customer behaviour analytics, machine-learning-driven website optimisation, dynamic content recommendations, product personalisation and extensive reporting. The app is better suited for larger enterprises with a significant investment in digital marketing.

    Matomo A/B Testing

    Matomo A/B testing page

    Matomo A/B Testing is a CRO tool, integrated into Matomo. All Matomo Cloud users get instant access to it, while On-Premise (free) Matomo users can purchase A/B testing as a plugin

    With Matomo A/B Testing, you can create multiple variations of a web or mobile page and test them with different segments of their audience. Matomo also doesn’t have any strict experiment caps, unlike Google Optimize. 

    You can split-test multiple creative variants for on-site assets such as buttons, slogans, titles, call-to-actions, image positions and more. You can even benchmark the performance of two (or more !) completely different homepage designs, for instance. 

    With us, you can compliantly and ethically collect historical user data about any visitor, who’s entered any of the active tests — and monitor their entire customer journey. You can also leverage Matomo A/B Testing data as part of multi-touch attribution modelling to determine which channels bring the best leads and which assets drive them towards conversion. 

     

    Since Matomo A/B Testing is part of our analytics platform, it works well with other features such as goal tracking, heatmaps, user session recordings and more. 

    Key features

    • Run experiments for web, mobile, email and digital campaigns 
    • Convenient A/B test design interface 
    • One-click experiment scheduling 
    • Integration with historic visitor profiles
    • Near real-time conversion tracking 
    • Apply segmentation to Matomo reports 
    • Easy creative variation sharing via a URL 

    Pros

    • High data accuracy with no reporting gaps 
    • Monitor the evolution of your success metrics for each variation
    • Embed experiments across multiple digital channels 
    • Set a custom confidence threshold for winning variations 
    • No compromises on user privacy 
    • Free 21-day trial available (for Matomo Cloud) and free 30-day plugin trial (for Matomo On-Premise)

    Cons

    • No on-site personalisation tools available 
    • Configuration requires some coding experience 

    Price : Matomo A/B Testing is included in the monthly Cloud plan (starting at €19 per month). On-Premise users can buy this functionality as a plugin (starting at €199/year). 

    Google Optimize vs Matomo A/B Testing : The Verdict 

    Matomo offers the same types of A/B testing features as Google Optimize (and some extras !), but without any usage caps. Unlike Matomo, Google Optimize doesn’t support A/B tests for mobile apps. You can access some content testing features for Android Apps via Firebase, but this requires another subscription. 

    Matomo lets you run A/B experiments across the web and mobile properties, plus desktop apps, email campaigns and digital ads. Also, Matomo has higher conversion data accuracy, thanks to our privacy-focused method for collecting website analytics

    When using Matomo in most EU markets, you’re legally exempt from showing a cookie consent banner. Meaning you can collect richer insights for each experiment and make data-driven decisions. Nearly 40% of global consumers reject cookie consent banners. With most other tools, you won’t be getting the full picture of your traffic. 

    Optimizely 

    Optimizely homepage

    Optimizely is a conversion optimization platform that offers several competitive products for a separate subscription. These include a flexible content management system (CMS), a content marketing platform, a web A/B testing app, a mobile featuring testing product and two eCommerce-specific website management products.

    The Web Experimentation app allows you to optimise every customer touchpoint by scheduling unlimited split or multi-variant tests and conversions across all your projects from the same app. Apart from websites, this subscription also supports experiments for single-page applications. But if you want more advanced mobile app testing features, you’ll have to purchase another product — Feature Experimentation. 

    Key features :

    • Intuitive experiment design tool 
    • Cross-browser testing and experiment preview 
    • Multi-page funnel tests design 
    • Behavioural and geo-targeting 
    • Exit/bounce rate tracking
    • Custom audience builder for experiments
    • Comprehensive reporting 

    Pros

    • Unlimited number of concurrent experiments 
    • Upload your audience data for test optimisation 
    • Dynamic content personalisation available on a higher tier 
    • Pre-made integrations with popular heatmap and analytics tools 
    • Supports segmentation by device, campaign type, traffic sources or referrer 

    Cons

    • You need a separate subscription for mobile CRO 
    • Free trial not available, pricing on-demand 
    • Multiple licences and subscriptions may be required 
    • Doesn’t support A/B tests for emails 

    Price : Available on-demand. 

    Web Experimentation tool has three subscription tiers — Grow, Accelerate, and Scale with different features included. 

    Google Optimize vs Optimizely : The Verdict 

    Optimizely is a strong contender for Google Optimize alternative as it offers more advanced audience targeting and segmentation options. You can target users by IP address, cookies, traffic sources, device type, browser, language, location or a custom utm_campaign parameter.

    Similar to Matomo A/B testing, Optimizely doesn’t limit the number of projects or concurrent experiments you can do. But you have to immediately sign an annual contract (no monthly plans are available). Pricing also varies based on the number of processed impressions (more experiments = a higher annual bill). An annual licence can cost $63,700 for 10 million impressions on average, according to an independent estimate. 

    Visual Website Optimizer (VWO) 

    VWO is another popular experimentation platform, supporting web, mobile and server-side A/B testing and personalisation campaigns.

    Similar to others, VWO offers a drag-and-drop visual editor for creating campaign variants. You don’t need design or coding knowledge to create tests. Once you’re all set, the app will benchmark your experiment performance against expected conversion rates, report on differences in conversion rate and point towards the best-performing creative. 

    Similar to Optimizely, VWO also offers web/mobile app optimisation as a separate subscription. Apart from testing visual page elements, you can also run in-app experiments throughout the product stack to locate new revenue opportunities. For example, you can test in-app subscription flows, search algorithms or navigation flows to improve product UX. 

    Key features :

    • Multivariate and multi-arm bandit tests 
    • Multi-step (funnel) split tests 
    • Collaborative experiment tracking dashboard 
    • Target users by different attributes (URL, device, geo-data) 
    • Personal library of creative elements 
    • Funnel analytics, session records, and heatmaps available 

    Pros

    • Free starter plan is available (similar to Google Optimize)
    • Simple tracking code installation and easy code editor
    • Offers online reporting dashboards and report downloads 
    • Slice-and-dice reports by different audience dimensions
    • No impact on website/app loading speed and performance 

    Cons

    • Multivariate testing is only available on a higher-tier plan 
    • Annual contract required, despite monthly billing 
    • Mobile app A/B split tests require another licence 
    • Requires ongoing user training 

    Price : Free limited plan available. 

    Then from $356/month, billed annually. 

    Google Optimize vs VWO : The Verdict 

    The free plan on VWO is very similar to Google Optimize. You get access to A/B testing and split URL testing features for websites only. The visual editing tool is relatively simple — and you can use URL or device targeting. 

    Free VWO reports, however, lack the advertised depth in terms of behavioural or funnel-based reporting. In-depth insights are available only to premium users. Extra advertised features like heatmaps, form analytics and session recordings require yet another subscription. With Matomo Cloud, you get all three of these together with A/B testing. 

    ConvertFlow 

    ConvertFlow Homepage

    ConvertFlow markets itself as a funnel optimisation app for eCommerce and SaaS companies. It meshes lead generation tools with some CRO workflows. 

    With ConvertFlow, you can effortlessly design opt-in forms, pop-ups, quizzes and even entire landing pages using pre-made web elements and a visual builder. Afterwards, you can put all of these assets to a “field test” via the ConvertFlow CRO platform. Select among pre-made templates or create custom variants for split or multivariate testing. You can customise tests based on URLs, cookie data and user geolocation among other factors. 

    Similar to Adobe Target, ConvertFlow also allows you to run tests targeted at specific customer segments in your CRM. The app has native integrations with HubSpot and Salesforce, so this feature is easy to enable. ConvertFlow also offers advanced targeting and segmentation options, based on user on-site behaviour, demographics data or known interests.

    Key features :

    • Create and test landing pages, surveys, quizzes, pop-ups, surveys and other lead-gen assets. 
    • All-in-one funnel builder for creating demand-generation campaigns 
    • Campaign personalisation, based on on-site activity 
    • Re-usable dynamic visitor segments for targeting 
    • Multi-step funnel design and customisation 
    • Embedded forms for split testing CTAs on existing pages 

    Pros

    • Allows controlling the traffic split for each variant to get objective results 
    • Pre-made integration with Google Analytics and Google Tag Manager 
    • Conversion and funnel reports, available for each variant 
    • Access to a library with 300+ conversion campaign templates
    • Apply progressive visitor profiling to dynamically adjust user experiences 

    Cons

    • Each plan covers only $10K views. Each extra 10k costs another $20/mo 
    • Only one website allowed per account (except for Teams plan) 
    • Doesn’t support experiments in mobile app 
    • Not all CRO features are available on a Pro plan. 

    Price : Access to CRO features costs from $300/month on a Pro plan. Subscription costs also increase, based on the total number of monthly views. 

    Google Optimize vs CovertFlow : The Verdict 

    ConvertFlow is equally convenient to use in conjunction with Google Analytics as Google Optimize is. But the similarities end up here since ConvertFlow combines funnel design features with CRO tools. 

    With ConvertFlow, you can run more advanced experiments and apply more targeting criteria than with Google Optimize. You can observe user behaviour and conversion rates across multi-step CTA forms and page funnels, plus benefit from first-touch attribution reporting without switching apps. 

    Though CovertFlow has a free plan, it doesn’t include access to CRO features. Meaning it’s not a free alternative to Google Optimize.

    Comparison of the Top 5 Google Optimize Alternatives

    FeatureGoogle OptimizeAdobe TargetMatomo A/B testOptimizely VWOConvertFlow

    Supported channelsWebWeb, mobile, social media, email Web, mobile, email, digital campaignsWebsites & mobile appsWebsites, web and mobile appsWebsites and mobile apps
    A/B testingcheck mark iconcheck mark iconcheck mark iconcheck mark iconcheck mark iconcheck mark icon
    Easy GA integration check mark iconXcheck mark iconcheck mark iconcheck mark iconcheck mark icon
    Integrations with other web analytics appsXXcheck mark iconcheck mark iconXcheck mark icon
    Audience segmentationBasicAdvancedAdvancedAdvancedAdvancedAdvanced
    Geo-targetingcheck mark iconcheck mark iconXcheck mark iconcheck mark iconcheck mark icon
    Behavioural targetingBasicAdvancedAdvancedAdvancedAdvancedAdvanced
    HeatmapsXXcheck mark icon

    No extra cost with Matomo Cloud
    〰️

    *via integrations
    〰️

    *requires another subscription
    X
    Session recordingsXXcheck mark icon

    No extra cost with Matomo Cloud
    X〰️

    *requires another subscription
    X
    Multivariate testing (MVT)check mark iconcheck mark iconcheck mark iconcheck mark iconcheck mark iconcheck mark icon
    Dynamic personalisation Xcheck mark iconXcheck mark icon〰️

    *only on higher account tiers
    〰️

    *only on the highest account tiers
    Product recommendationsXcheck mark iconX〰️

    *requires another subscription
    〰️

    *requires another subscription
    check mark icon
    SupportSelf-help desk on a free tierEmail, live-chat, phone supportEmail, self-help guides and user forumKnowledge base, online tickets, user communitySelf-help guides, email, phoneKnowledge base, email, and live chat support
    PriceFreemiumOn-demandFrom €19 for Cloud subscription

    From €199/year as plugin for On-Premise
    On-demandFreemium

    From $365/mo
    From $300/month

    Conclusion 

    Google Optimize has served marketers well for over five years. But as the company decided to move on — so should you. 

    Oher A/B testing tools like Matomo, Optimizely or VWO offer better funnel analytics and split testing capabilities without any usage caps. Also, tools like Adobe Target, Optimizely, and VWO offer advanced content personalisation, based on aggregate analytics. However, they also come with much higher subscription costs.

    Matomo is a robust, compliant and cost-effective alternative to Google Optimize. Our tool allows you to schedule campaigns across all digital mediums (and even desktop apps !) without a

  • Playing Video on a Sega Dreamcast

    9 mars 2011, par Multimedia Mike — Sega Dreamcast

    Here’s an honest engineering question : If you were tasked to make compressed video play back on a Sega Dreamcast video game console, what video format would you choose ? Personally, I would choose RoQ, the format invented for The 11th Hour computer game and later used in Quake III and other games derived from the same engine. This post explains my reasoning.

    Video Background
    One of the things I wanted to do when I procured a used Sega Dreamcast back in 2001 was turn it into a set-top video playback unit. This is something that a lot of people tried to do, apparently, to varying degrees of success. Interest would wane in a few years as it became easier and easier to crack an Xbox and install XBMC. The Xbox was much better suited to playing codecs that were getting big at the time, most notably MPEG-4 part 2 video (DivX/XviD).

    The Dreamcast, while quite capable when it was released in 1999, was not very well-equipped to deal with an MPEG-type codec. I have recently learned that there are other hackers out there on the internet who are still trying to get the most out of this system. I was contacted for advice about how to make Theora perform better on the Dreamcast.

    Interesting thing about consoles and codecs : Since you are necessarily distributing code along with your data, you have far more freedom to use whatever codecs you want for your audio and video data. This is why Vorbis and even Theora have seen quite a bit of use in video games, "internet standards" be darned. Thus, when I realized this application had no hard and fast requirement to use Theora, and that it could use any codec that fit the platform, my mind started churning. When I was programming the DC 10 years ago, I didn’t have access to the same wealth of multimedia knowledge that is currently available.

    Requirements Gathering
    What do we need here ?

    • Codec needs to run on the Sega Dreamcast ; this eliminates codecs for which only binary decoder implementations are available
    • Must decode 320x240 video at 30 fps ; higher resolutions up to 640x480 would be desirable
    • Must deliver decent quality at 12X optical read speeds (DC drive speed)
    • There must be some decent, preferably free, encoder readily available ; speed of encoding, however, is not important ; i.e., "take as long as you need, encoder"

    Theora was the go-to codec because it’s just commonly known as "the free, open source video codec". But clearly it’s not suitable for, well... any purpose, really (sorry, easy target ; OW ! stop throwing things !). VP8/WebM — Theora’s heir apparent — would not qualify either, as my prior experiments have already demonstrated.

    Candidates
    What did the big boys use for video on the Dreamcast ? A lot of games relied on CRI’s Sofdec middleware which was MPEG-1 video and a custom ADPCM format. I don’t know if I have ever seen DC games that used MPEG-1 video at a higher resolution than 320x240 (though I have not searched exhaustively). The fact that CRI used a custom ADPCM format for this application may indicate that there wasn’t enough CPU power left over to decode a perceptual, transform-based audio codec alongside the 320x240 video.

    A few other DC games used 4X Technologies’ 4XM format. The most notable licensee was Alone in the Dark : The New Nightmare (DC version only ; PC version used Bink). This codec was DCT-based but incorporated 16-bit RGB colorspace into its design, presumably to optimize for applications like game consoles that couldn’t directly handle planar YUV. AITD:TNN’s videos were 640x360, a marked improvement over the typical Sofdec fare. I was about to write off 4XM as a contender due to lack of encoder, but the encoding tools are preserved on our samples site. A few other issues, though : The FFmpeg decoder doesn’t seem to work correctly as of this writing (and nobody has noticed yet, even though it’s tested via FATE).

    What ideas do I have ? Right off the bat, I’m thinking vector quantizer (VQ). Vector quantizers are notoriously slow to compress but are blazingly fast to decompress which is why they were popular in the early days of video compression. First, there’s Cinepak. I fear that might be too simple for this application. Plus, I don’t know if existing (binary-only) compressors are very decent. It seems that they only ever had to handle small videos and I’ve heard that they can really fall over if anything more is demanded of them.

    Sorenson Video 1 is another contender. FFmpeg has an encoder (which some allege is better than Sorenson’s original compressor). However, I fear that the wonky algorithm and colorspace might not mesh well with the Dreamcast.

    My thinking quickly converged on RoQ. This was designed to run fullscreen (640x480) video on i486-class hardware. While RoQ fundamentally operates in a YUV colorspace, it’s trivial to convert it to any other colorspace during decoding and the image will be rendered in that colorspace. Plus, there are open source encoders available for the format (namely, several versions of Eric Lasota’s Switchblade encoder, one of which lives natively in FFmpeg), as well as the original proprietary encoder.

    Which Library ?
    There are several code choices here : FFmpeg (LGPL), Switchblade (GPL), and the original Quake 3 source code (GPL). There is one more option that I think might be easiest, which is the decoder Dr. Tim created when he reverse engineered the format in the first place. That has a very liberal "do whatever you like, but be nice and give me credit" license (probably qualifies as BSD).

    This code is no longer at its original home but the Wayback Machine still had a copy, which I have now mirrored (idroq.tar.gz).

    Adaptation
    Dr. Tim’s code still compiles and runs great on Linux (64-bit !) with SDL output. I would like to get it ported to the Dreamcast using the same SDL output, which KallistiOS supports. Then, there is the matter of fixing the longstanding chroma bug in the original sample decoder (described here). The decoder also needs to be modified to natively render RGB565 data, as that will work best with the DC’s graphics hardware.

    After making the code work, I want to profile it and test whether it can handle full-frame 640x480 playback at 30 frames/second. I will need to contrive a sample to achieve this.

    Unfortunately, things went off the rails pretty quickly when I tried to get the RoQ decoder ported to DC/KOS. It looks like there’s a bug in KallistiOS’s minimalistic standard C library, or at least a discrepancy with my desktop Linux system. When you read to the end of a file and then seek backwards to someplace that isn’t the end, is the file still in EOF state ?

    According to my Linux desktop :

    open file ;          feof() = 0
    seek to end ;        feof() = 0
    read one more byte ; feof() = 1
    seek back to start ; feof() = 0
    

    According to KallistiOS :

    open file ;          feof() = 0
    seek to end ;        feof() = 0
    read one more byte ; feof() = 1
    seek back to start ; feof() = 1
    

    Here’s the seek-test.c program I used to test this issue :

    C :
    1. #include <stdio .h>
    2.  
    3. int main()
    4. {
    5.   FILE *f ;
    6.   unsigned char byte ;
    7.  
    8.   f = fopen("seek_test.c", "r") ;
    9.   printf("open file ;     feof() = %d\n", feof(f)) ;
    10.   fseek(f, 0, SEEK_END) ;
    11.   printf("seek to end ;    feof() = %d\n", feof(f)) ;
    12.   fread(&byte, 1, 1, f) ;
    13.   printf("read one more byte ; feof() = %d\n", feof(f)) ;
    14.   fseek(f, 0, SEEK_SET) ;
    15.   printf("seek back to start ; feof() = %d\n", feof(f)) ;
    16.   fclose(f) ;
    17.  
    18.   return 0 ;
    19. }

    EOF
    Speaking of EOF, I’m about done for this evening.

    What codec would you select for this task, given the requirements involved ?

  • Zlib vs. XZ on 2SF

    21 juillet 2012, par Multimedia Mike — General, psf, saltygme, xz, zlib

    I recently released my Game Music Appreciation website. It allows users to play an enormous range of video game music directly in their browsers. To do this, the site has to host the music. And since I’m a compression bore, I have to know how small I can practically make these music files. I already published the results of my effort to see if XZ could beat RAR (RAR won, but only slightly, and I still went with XZ for the project) on the corpus of Super Nintendo chiptune sets. Next is the corpus of Nintendo DS chiptunes.

    Repacking Nintendo DS 2SF
    The prevailing chiptune format for storing Nintendo DS songs is the .2sf format. This is a subtype of the Portable Sound Format (PSF). The designers had the foresight to build compression directly into the format. Much of payload data in a PSF file is compressed with zlib. Since I already incorporated Embedded XZ into the player project, I decided to try repacking the PSF payload data from zlib -> xz.

    In an effort to not corrupt standards too much, I changed the ’PSF’ file signature (seen in the first 3 bytes of a file) to ’psf’.

    Results
    There are about 900 Nintendo DS games currently represented in my website’s archive. Total size of the original PSF archive, payloads packed with zlib : 2.992 GB. Total size of the same archive with payloads packed as xz : 2.059 GB.

    Using xz vs. zlib saved me nearly a gigabyte of storage. That extra storage doesn’t really impact my hosting plan very much (I have 1/2 TB, which is why I’m so nonchalant about hosting the massive MPlayer Samples Archive). However, smaller individual files translates to a better user experience since the files are faster to download.

    Here is a pretty picture to illustrate the space savings :



    The blue occasionally appears to dip below the orange but the data indicates that xz is always more efficient than zlib. Here’s the raw data (comes in vanilla CSV flavor too).

    Interface Impact
    So the good news for the end user is that the songs are faster to load up front. The downside is that there can be a noticeable delay when changing tracks. Even though all songs are packaged into one file for download, and the entire file is downloaded before playback begins, each song is individually compressed. Thus, changing tracks triggers another decompression operation. I’m toying the possibility of some sort of background process that decompresses song (n+1) while playing song (n) in order to help compensate for this.

    I don’t like the idea of decompressing everything up front because A) it would take even longer to start playing ; and B) it would take a huge amount of memory.

    Corner Case
    There was at least one case in which I found zlib to be better than xz. It looks like zlib’s minimum block size is smaller than xz’s. I think I discovered xz to be unable to compress a few bytes to a block any smaller than about 60-64 bytes while zlib got it down into the teens. However, in those cases, it was more efficient to just leave the data uncompressed anyway.