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• avformat/smacker : Improve timestamps

  24 juin 2020, par Andreas Rheinhardt

  avformat/smacker : Improve timestamps
  A Smacker file can contain up to seven audio tracks. Up until now,
  
  the pts for the i. audio packet contained in a Smacker frame was
  
  simply the end timestamp of the last i. audio packet contained in
  
  an earlier Smacker frame.
  The problem with this is that a Smacker stream need not contain data in
  
  every Smacker frame and so the current i. audio packet present may come
  
  from a different underlying stream than the last i. audio packet
  
  contained in an earlier frame.
  The sample hypnotix.smk* exhibits this. It has three audio tracks and
  
  the first of the three has a longer first packet, so that the audio for
  
  the first track is contained in only 235 packets contained in the first
  
  235 Smacker frames ; the end timestamp of this track is 166696 (about 7.56s
  
  at a timebase of 1/22050) ; the other two audio tracks both have 253 packets
  
  contained in the first 253 Smacker frames. Up until now, the 236th
  
  packet of the second track being the first audio packet in the 236th
  
  Smacker frame would get the end timestamp of the last first audio packet
  
  from the last Smacker frame containing a first audio packet and said
  
  last audio packet is the first audio packet from the 235th Smacker frame
  
  from the first audio track, so that the timestamp is 166696. In contrast,
  
  the 236th packet from the third track (whose packets contain the same number
  
  of samples as the packets from the second track) has a timestamp of
  
  156116 (because its timestamp is derived from the end timestamp of the
  
  235th packet of the second audio track). In the end, the second track
  
  ended up being 177360/22050 s = 8.044s long ; in contrast, the third
  
  track was 166780/22050 s = 7.56s long which also coincided with the
  
  video.
  This commit fixes this by not using timestamps from other tracks for
  
  a packet's pts.
  * : https://samples.ffmpeg.org/game-formats/smacker/wetlands/hypnotix.smk
  Reviewed-by : Timotej Lazar <timotej.lazar@araneo.si>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/smacker.c

• 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 :

  PLAIN TEXT

  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 ?

• Homepage Design : Best Practices & Examples

  5 octobre 2022, par Erin

  Did you know users spend about 50 milliseconds deciding if they like your website’s homepage design or not ?

  With billions of websites and scrolling often done on the go, you have to make a strong first impression because the chances for a once-over are slim. 

  Learn how to design magnetically-appealing website homepages from this guide. 

  What is a homepage in web design ?

  Homepage is the front page of your website — a destination where users land when typing your website URL address. It’s located at the root of the website’s domain (e.g., matomo.org) or a subdomain (e.g., university.webflow.com).

  Design-wise a homepage has two goals :

  • Explain the purpose of the website and present overview information 
  • Provide top-level navigation to lower-level web pages (e.g., blog, sales pages, etc.) 

  Separately, a homepage is also the place where users will return each time they’ll feel stuck and want to start anew. Thus, your homepage website design should provide obvious navigation paths to other website areas.

  6 Must-Know Website Homepage Design Best Practices

  Behind every winning homepage design stands a detailed customer journey map. 

  A customer journey is a schematic representation of how site visitors will move around your website to accomplish various goals. 

  A good customer journey map lists different actions a user will take after landing on your website (e.g., browse product pages, save items to a wishlist, register an account, etc.) — and it does so for different audience segments. 

  

  Your homepage design should help users move from the first step on their journey (e.g., learning about your website) to the final one (e.g., converting to a paid customer). At the same time, your homepage should serve the needs of both new and returning visitors — prospects who may be at a different stage of their journey (e.g., consideration). 

  With the above in mind, let’s take a look at several website homepage design ideas and the reasons why they work. 

  1. Use Familiar Design Elements

  Whether you’re designing a new website or refreshing an old one, it’s always tempting to go “out of the box” — use horizontal scrolling, skip header navigation or include arty animations. 

  Bold design choices work for some brands, mainly those who aren’t using their website as a primary sales channel (e.g., luxury brands). 

  But unfamiliar design patterns can also intimidate a lot of shoppers. In one observational study, people were asked to guess where specific content (e.g., information on international calls) would be placed on a telecom website. 75% of users picked the same location. This means two things :

  • People already have expectations of where specific website information is typically placed 
  • Yet, one in four users struggles to identify the right areas even within standard website layouts

  So why make the job harder for them ? As UX consultant Peter Ramsey rightfully notes : 

  The truth is : designing the best experience isn’t about being unique, it’s about being easy. And guess what feels really easy to use ? Things that feel familiar.

  Therefore, analyse other homepage layout designs in your industry. Pay attention to the number and type of homepage screens and approaches to designing header/footer navigation. 

  Take some of those ideas as your “base”. Then make your homepage design on-brand with unique typography, icons, visuals and other graphic design elements.

  Take a cue from ICAM — a steel manufacturing company. Their niche isn’t typically exciting. Yet, their homepage design stops you in your tracks and tinkers your curiosity to discover more (even if you aren’t shopping for metalware). 

  

  The interesting part is that ICAM uses a rather standard homepage layout. You have a hero image in the first screen, followed by a multi-column layout of their industry expertise and an overview of manufacturers. 

  But this homepage design feels fresh because the company uses plenty of white space, bold typography and vibrant visuals. Also, they delay the creative twist (horizontal scrolling area) to the bottom of the homepage, meaning that it’s less likely to intimidate less confident web users. 

  2. Decide On The Optimal Homepage Layout 

  In web design, a homepage layout is your approach to visually organising different information on the screen. 

  Observant folks will notice that good homepage designs often have the same layout. For example, include a split-view “hero” screen with a call to action on the left and visuals (photo or video) on the left. 

  

  The reason for using similar layouts for website homepage design isn’t a lack of creativity. On the contrary, some layouts have become the “best practice” because they :

  • Offer a great user experience (UX) and don’t confuse first-time visitors 
  • Feel familiar and create a pleasurable sense of deja-vu among users 
  • Have proven to drive higher conversion rates through benchmarks and tests 

  Popular types of website homepage layouts : 

  • Single column – a classic option of presenting main content in a single, vertical column. Good choice for blogs, personal websites and simple corporate sites. 
  • Split screen layout divides the page in two equal areas with different information present. Works best for Ecommerce homepages (e.g., to separate different types of garments) or SaaS websites, offering two product types (e.g., a free personal product version and a business edition). 
  • Asymmetrical layout assumes dividing your homepage into areas of different size and styles. Asymmetry helps create specific focal points for users to draw their attention to the most prominent information. 
  • Grid of cards layout helps present a lot of information in a more digestible manner by breaking down bigger bulks of text into smaller cards — a graphic element, featuring an image and some texts. By tapping a card, users can then access extra content. 
  • Boxes are visually similar to cards, but can be of varying shape. For example, you can have a bigger header-width box area, followed by four smaller boxes within it. Both of these website layouts work well for Ecommerce. 
  • Featured image layout gives visuals (photos and videos) the most prominent placement on the homepage, with texts and other graphic design elements serving a secondary purpose. 
  • F-pattern layout is based on the standard eye movement most people have when reading content on the website. Eye tracking studies found that we usually pay the most attention to information atop of the page (header area), then scan horizontally before dripping down to the next vertical line until we find content that captures our attention. 

  User behaviour analytics (UBA) tools are the best way to determine what type of layout will work for your homepage. 

  For example, you can use Matomo Heatmaps and Session Recording to observe how users navigate your homepage, which areas or links they click and what blockers they face during navigation.

  

  Matomo can capture accurate behavioural insights because we track relative positions to elements within your websites. This approach allows us to provide accurate data for users with different browsers, operating systems, zoom-in levels and fonts. 

  The best part ? You can collect behavioural data from up to 100 different user segments to understand how different audience cohorts engage with your product.

  3. Include a One-Sentence Tagline

  A tagline is a one-line summary of what your company does and what its unique sales proposition (USP) is. It should be short, catchy and distinguish you from competitors.

  A modern homepage design practice is to include a call to action in the first screen. Why ? Because you then instantly communicate or remind of your value proposition to every user — and provide them with an easy way to convert whenever they are ready to do business with you. 

  Here’s how three companies with a similar product, a project management app, differentiate themselves through homepage taglines. 

  Monday.com positions itself as an operating system (OS) for work. 

  

  Basecamp emphasises its product simplicity and openly says that they are different from other overly-complex software. 

  

  Asana, in turn, addresses a familiar user pain point (siloed communication) that it attempts to fix with its product. 

  

  Coming up with the perfect homepage tagline is a big task. You may have plenty of ideas, but little confidence in what version will stick. 

  The best approach ? Let a series of A/B tests decide. You can test a roaster of homepage slogans on a rotating bi-weekly/monthly schedule and track how copy changes affect conversion rates. 

  With Matomo A/B test feature, you can create, track and manage all experiments straight from your web analytics app — and get consolidated reports on total page visitors and conversion rates per each tested variation. 

  

  Beyond slogans, you can also run A/B tests to validate submission form placements, button texts or the entire page layout. 

  For instance, you can benchmark how your new homepage design performs compared to the old version with a subset of users before making it publicly available. 

  4. Highlight The Main Tasks For The User

  Though casual browsing is a thing, most of us head to specific websites with a clear agenda — find information, compare prices, obtain services, etc. 

  Thus, your homepage should provide clear starting points for users’ main tasks (those you’ve also identified as conversion goals on your customer journey maps !).

  These tasks can include : 

  • Account registration 
  • Product demo request 
  • Newsletter sign-up 

  The best website homepage designs organically guide users through a set number of common tasks, one screen at a time. 

  Let’s analyse Sable homepage design. The company offers a no-fee bank account and a credit card product for soon-to-be US transplants. The main task a user has : Decide if they want to try Sable and hopefully open an account with them. 

  

  This mono-purpose page focuses on persuading a prospect that Sable is right for them. 

  The first screen hosts the main CTA with an animated drop-down arrow to keep scrolling. This is likely aimed at first-time visitors that just landed on the page from an online ad or social media post. 

  The second screen serves the main pitch — no-fee, no-hassle access to a US banking account that also helps you build your credit score. 

  The third screen encourages users to learn more about Sable Credit — the flagship product. For the sceptics, the fourth screen offers several more reasons to sign up for the credit product. 

  Then Sable moves on to pitching its second offering — a no-fee debit card with a cashback. Once again, the follow-up screen sweetens the deal by bringing up other perks (higher cashback for popular services like Amazon) and overcoming objections (no SSN required and multi-language support available). 

  The sequence ends with side-by-side product comparison and some extra social proof. 

  In Sable’s case, each homepage screen has a clear purpose and is designed to facilitate one specific user action — account opening. 

  For multi-product companies, the above strategy works great for designing individual landing pages. 

  5. Design Proper Navigation Paths

  All websites have two areas reserved for navigation : 

  • Header menu 
  • Footer menu 

  Designing an effective header menu is more important since it’s the primary tool visitors will use to discover other pages. 

  Your header menu can be :

  • Sticky — always visible as the person keeps scrolling. 
  • Static — e.g., a hidden drop-down menu. 

  If you go for a static header and have a longer homepage layout (e.g., 5+ screens), you also need to add extra navigation elements somewhere mid-page. Or else users might not figure out where to go next and merely bounce off. 

  You can do this by : 

  • Promoting other areas of your website (e.g., sub-category pages) by linking out to them 
  • Adding a carousel of “recent posts”, “recommended reads” and “latest products” 
  • Using buttons and CTAs to direct users towards specific actions (e.g., account registration) or assets (free eBook)

  For instance, cosmetics brand Typology doesn’t have a sticky header on the homepage. Instead, they prompt discovery by promoting different product categories (best sellers, bundles, latest arrivals) and their free skin diagnostic quiz — a great engagement mechanism to retain first time users.

  

  Once the user scrolls down to the bottom of the page, they should have an extra set of navigational options — aka footer links. 

  Again, these help steer the visitor towards discovering more content without scrolling back up to the top of your homepage. 

  Nielsen Norman Group says that people mostly use footers as :

  • A second chance to be convinced — after reading the entire homepage, the user is ready to give your product a go.
    
  • The last resort for hard-to-find content that’s not displayed in global header navigation (e.g., Terms and Conditions or shipping information pages).

  As a rule of thumb, you should designate the following information to the footer : 

  • Utility links (Contact page, Terms & Conditions, Privacy Policy, etc.) 
  • Secondary-task links (e.g., Career page, Investor Details, Media contacts, etc.) 
  • Brands within the organisation (if you operate several) 
  • Customer engagement link (email newsletters and social media buttons)

  The key is to keep the area compact — not more than one standard user screen resolution of 1280×720. 

  6. Show Users What’s Clickable (Or Not) 

  A homepage invites your site visitors on a journey. But if they don’t know which elements to click, they aren’t going to get anywhere.

  Good homepage design makes it obvious which page elements are clickable, i.e., can take the user to a new page or another segment of the homepage. 

  Here are several must-know homepage design tips for better on-page navigation : 

  • Use colour and underline or bold to highlight clickable words. Alternatively, you can change the browser cursor from a standard arrow into another element (e.g., a larger dot or a pointy finger) to indicate when the cursor hovers over a clickable website area. 
  • Make descriptive button texts that imply what will happen when a user clicks the page. Instead of using abstract and generic button texts like “see more” or “learn more”, try a more vibrant language like “dive in” for clicking through to a spa page. 
  • Use a unified hover area to show how different homepage design elements represent a single path or multiple navigation paths. When multiple items are encapsulated in one visual element (e.g., a box), users may be reluctant to click the image because they aren’t sure if it’s one large hit area leading to a single page or if there are multiple hit areas, leading to different pages. 

  Homepage of BEAUSiTE — a whimsical hotel in the Swiss Alps – embodies all of the above design principles. They change the cursor style whenever you scroll into a hit area, use emotive and creative micro-copy for all button texts and clearly distinguish between different homepage elements.

  

  How to Make Your Homepage Design Even More Impactful ? 

  Website homepage design is roughly 20% of pure design work and 80% of behind-the-scenes research. 

  To design a high-performing homepage you need to have data-backed answers to the following questions : 

  • Who are your primary and secondary target audiences ? 
  • Which tasks (1 to 4) you’d want to help them solve through your homepage ?

  You can get the answers to both questions from your web analytics data by using audience segmentation and page transition (behaviour flow) reports in Matomo. 

  Based on these, you can determine common user journeys and tasks people look to accomplish when visiting your website. Next, you can collect even more data with UBA tools  like heatmaps and user session recordings. Then translated the observed patterns into working homepage design ideas. 

  Improve your homepage design and conversion rates with Matomo. Start your free 21-day trial now ! 

  21 day free trial. No credit card required.

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