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• When I use ffmpeg to go from a video to frames, and then back to video, the duration is different between the videos

  24 février 2024, par bluepanda

  I am trying to use ffmpeg to convert from a .mp4 (or .mov) video into individual frames, do some processing on those frames, and then convert back to .mp4. The problem is that the resulting video I create is a different duration than the input - I can see this visually when I play the two videos side by side. The difference is not large (i.e. 00:00:00.50 for the input video and 00:00:00.52 for the output video), but when the videos are looped next to each other they get out of sync.

  


  Here is information about the input video retrieved using fluent-ffmpeg's ffmpeg.ffprobe(videoPath) :

  


  metadata {
  streams: [
    {
      index: 0,
      codec_name: 'h264',
      codec_long_name: 'H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10',
      profile: 'High',
      codec_type: 'video',
      codec_tag_string: 'avc1',
      codec_tag: '0x31637661',
      width: 1080,
      height: 1920,
      coded_width: 1080,
      coded_height: 1920,
      closed_captions: 0,
      has_b_frames: 2,
      sample_aspect_ratio: 'N/A',
      display_aspect_ratio: 'N/A',
      pix_fmt: 'yuv420p',
      level: 40,
      color_range: 'tv',
      color_space: 'bt709',
      color_transfer: 'bt709',
      color_primaries: 'bt709',
      chroma_location: 'left',
      field_order: 'unknown',
      refs: 1,
      is_avc: 'true',
      nal_length_size: 4,
      id: 'N/A',
      r_frame_rate: '30000/1001',
      avg_frame_rate: '27000/1001',
      time_base: '1/30000',
      start_pts: 0,
      start_time: 0,
      duration_ts: 15100,
      duration: 0.503333,
      bit_rate: 5660223,
      max_bit_rate: 'N/A',
      bits_per_raw_sample: 8,
      nb_frames: 36,
      nb_read_frames: 'N/A',
      nb_read_packets: 'N/A',
      tags: [Object],
      disposition: [Object]
    },
    {
      index: 1,
      codec_name: 'aac',
      codec_long_name: 'AAC (Advanced Audio Coding)',
      profile: 'LC',
      codec_type: 'audio',
      codec_tag_string: 'mp4a',
      codec_tag: '0x6134706d',
      sample_fmt: 'fltp',
      sample_rate: 48000,
      channels: 2,
      channel_layout: 'stereo',
      bits_per_sample: 0,
      id: 'N/A',
      r_frame_rate: '0/0',
      avg_frame_rate: '0/0',
      time_base: '1/48000',
      start_pts: 0,
      start_time: 0,
      duration_ts: 24160,
      duration: 0.503333,
      bit_rate: 248416,
      max_bit_rate: 'N/A',
      bits_per_raw_sample: 'N/A',
      nb_frames: 27,
      nb_read_frames: 'N/A',
      nb_read_packets: 'N/A',
      tags: [Object],
      disposition: [Object]
    }
  ],
  format: {
    filename: '/Users/name/images/input.mp4',
    nb_streams: 2,
    nb_programs: 0,
    format_name: 'mov,mp4,m4a,3gp,3g2,mj2',
    format_long_name: 'QuickTime / MOV',
    start_time: 0,
    duration: 0.503333,
    size: 963879,
    bit_rate: 15319941,
    probe_score: 100,
    tags: {
      major_brand: 'mp42',
      minor_version: '1',
      compatible_brands: 'isommp41mp42',
      creation_time: '2024-02-14T01:21:12.000000Z'
    }
  },
  chapters: []
}


  


  and here is from running ffprobe directly :

  


  ffprobe '/Users/name/images/input.mp4'
ffprobe version 6.1.1 Copyright (c) 2007-2023 the FFmpeg developers
  built with Apple clang version 15.0.0 (clang-1500.1.0.2.5)
  configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/6.1.1_2 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags='-Wl,-ld_classic' --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libaribb24 --enable-libbluray --enable-libdav1d --enable-libharfbuzz --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopenvino --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-audiotoolbox --enable-neon
  libavutil      58. 29.100 / 58. 29.100
  libavcodec     60. 31.102 / 60. 31.102
  libavformat    60. 16.100 / 60. 16.100
  libavdevice    60.  3.100 / 60.  3.100
  libavfilter     9. 12.100 /  9. 12.100
  libswscale      7.  5.100 /  7.  5.100
  libswresample   4. 12.100 /  4. 12.100
  libpostproc    57.  3.100 / 57.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/Users/name/images/input.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 1
    compatible_brands: isommp41mp42
    creation_time   : 2024-02-14T01:21:12.000000Z
  Duration: 00:00:00.50, start: 0.000000, bitrate: 15319 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 1080x1920, 5660 kb/s, 26.97 fps, 29.97 tbr, 30k tbn (default)
    Metadata:
      creation_time   : 2024-02-14T01:21:12.000000Z
      handler_name    : Core Media Video
      vendor_id       : [0][0][0][0]
      encoder         : AVC Coding
  Stream #0:1[0x2](und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 248 kb/s (default)
    Metadata:
      creation_time   : 2024-02-14T01:21:12.000000Z
      handler_name    : Core Media Audio
      vendor_id       : [0][0][0][0]


  


  And this is my command to go from video to frames :

  


  ffmpeg -i /Users/name/images/input.mp4 -y -f image2 /Users/name/images/frames/%d.png


  


  After which I convert the frames back to video with this - note that I get by seeing avg_frame_rate is 27000/1001 = 26.97302697 :

  


  ffmpeg -r 26.973026973026972 -i /Users/name/images/frames/%d.png -y -r 26.973026973026972 -b:v 5660223k -f mp4 -pix_fmt yuv420p -t 0.503333 /Users/name/images/output.mp4


  


  And if I then run fluent-ffmpeg's ffmpeg.ffprobe(videoPath) I get :

  


  metadata {
  streams: [
    {
      index: 0,
      codec_name: 'h264',
      codec_long_name: 'H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10',
      profile: 'High',
      codec_type: 'video',
      codec_tag_string: 'avc1',
      codec_tag: '0x31637661',
      width: 1080,
      height: 1920,
      coded_width: 1080,
      coded_height: 1920,
      closed_captions: 0,
      has_b_frames: 2,
      sample_aspect_ratio: '1:1',
      display_aspect_ratio: '9:16',
      pix_fmt: 'yuv420p',
      level: 62,
      color_range: 'unknown',
      color_space: 'unknown',
      color_transfer: 'unknown',
      color_primaries: 'unknown',
      chroma_location: 'left',
      field_order: 'unknown',
      refs: 1,
      is_avc: 'true',
      nal_length_size: 4,
      id: 'N/A',
      r_frame_rate: '27000/1001',
      avg_frame_rate: '27000/1001',
      time_base: '1/27000',
      start_pts: 0,
      start_time: 0,
      duration_ts: 14014,
      duration: 0.519037,
      bit_rate: 52138429,
      max_bit_rate: 'N/A',
      bits_per_raw_sample: 8,
      nb_frames: 14,
      nb_read_frames: 'N/A',
      nb_read_packets: 'N/A',
      tags: [Object],
      disposition: [Object]
    }
  ],
  format: {
    filename: '/Users/name/images/output.mp4',
    nb_streams: 1,
    nb_programs: 0,
    format_name: 'mov,mp4,m4a,3gp,3g2,mj2',
    format_long_name: 'QuickTime / MOV',
    start_time: 0,
    duration: 0.52,
    size: 3383708,
    bit_rate: 52057046,
    probe_score: 100,
    tags: {
      major_brand: 'isom',
      minor_version: '512',
      compatible_brands: 'isomiso2avc1mp41',
      encoder: 'Lavf60.3.100'
    }
  },
  chapters: []
}


  


  and here is from running ffprobe directly :

  


  ffprobe '/Users/name/images/output.mp4'
ffprobe version 6.1.1 Copyright (c) 2007-2023 the FFmpeg developers
  built with Apple clang version 15.0.0 (clang-1500.1.0.2.5)
  configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/6.1.1_2 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags='-Wl,-ld_classic' --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libaribb24 --enable-libbluray --enable-libdav1d --enable-libharfbuzz --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopenvino --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-audiotoolbox --enable-neon
  libavutil      58. 29.100 / 58. 29.100
  libavcodec     60. 31.102 / 60. 31.102
  libavformat    60. 16.100 / 60. 16.100
  libavdevice    60.  3.100 / 60.  3.100
  libavfilter     9. 12.100 /  9. 12.100
  libswscale      7.  5.100 /  7.  5.100
  libswresample   4. 12.100 /  4. 12.100
  libpostproc    57.  3.100 / 57.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/Users/name/images/output.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf60.3.100
  Duration: 00:00:00.52, start: 0.000000, bitrate: 52153 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1080x1920 [SAR 1:1 DAR 9:16], 52138 kb/s, 26.97 fps, 26.97 tbr, 27k tbn (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : Lavc60.3.100 libx264


  


  This seems like it should be a fairly common scenario, but I have not been able to find examples of this, and the other questions about incorrect durations on Stack Overflow are about bigger differences (i.e. 3 seconds instead of 10 seconds : Wrong video duration when recording with ffmpeg).

  


  Some other details :

  


  

  • I am running this through a Node.js script with fluent-ffmpeg, but I have also tried running the commands directly in the terminal and the result is the same.

  


  • I am fine with the output frames being .png / .jpg / other formats.

  


  • I am fine with setting this to a different frame rate than the original as long as the two output videos end up with the same duration.

  


  • One suspicious thing is that I set -t 0.503333 when creating the video, but it doesn't seem to work as the result video shows duration: 0.519037 / 00:00:00.52.

  


  


  Thank you for any help !

  


• 6 Crucial Benefits of Conversion Rate Optimisation

  26 février 2024, par Erin

  Whether investing time or money in marketing, you want the best return on your investment. You want to get as many customers as possible with your budget and resources.

  That’s what conversion rate optimisation (CRO) aims to do. But how does it help you achieve this major goal ? 

  This guide explores the concrete benefits of conversion rate optimisation and how they lead to more effective marketing and ROI. We’ll also introduce specific CRO best practices to help unlock these benefits.

  What is conversion rate optimisation ?

  Conversion rate optimisation (CRO) is the process of examining your website for improvements and creating tests to increase the number of visitors who take a desired action, like purchasing a product or submitting a form.

  The conversion rate is the percentage of visitors who complete a specific goal.

  

  In order to improve your conversion rate, you need to figure out :

  • Where your customers come from
  • How potential customers navigate or interact with your website
  • Where potential customers are likely to exit your site (or abandon carts)
  • What patterns drive valuable actions like sign-ups and sales

  From there, you can gradually implement changes that will drive more visitors to convert. That’s the essence of conversion rate optimisation.

  6 top benefits of conversion rate optimisation (and best practices to unlock them)

  Conversion rate optimisation can help you get more out of your campaigns without investing more. CRO helps you in these six ways :

  1. Understand your visitors (and customers) better

  The main goal of CRO is to boost conversions, but it’s more than that. In the process of improving conversion rates, you’ll also benefit by gaining deep insights into user behaviour, preferences, and needs. 

  Using web analytics, tests and behavioural analytics, CRO helps marketers shape their website to match what users need.

  Best practices for understanding your customer :

  First, analyse how visitors act with full context (the pages they view, how long they stay and more). 

  In Matomo, you can use the Users Flow report to understand how visitors navigate through your site. This will help you visualise and identify trends in the buyer’s journey.

  

  Then, you can dive deeper by defining and analysing journeys with Funnels. This shows you how many potential customers follow through each step in your defined journey and identify where you might have a leaky funnel. 

  

  In the above Funnel Report, nearly half of our visitors, just 44%, are moving forward in the buyer’s journey after landing on our scuba diving mask promotion page. With 56% of potential customers dropping off at this page, it’s a prime opportunity for optimising conversions.

  Think of Funnels as your map, and pages with high drop-off rates as valuable opportunities for improvement.

  Once you notice patterns, you can try to identify the why. Analyse the pages, do user testing and do your best to improve them.

  2. Deliver a better user experience

  A better understanding of your customers’ needs means you can deliver a better user experience.

  

  For example, if you notice many people spend more time than expected on a particular step in the sign-up process, you can work to streamline it.

  Best practices for improving your user experience : 

  To do this, you need to come up with testable hypotheses. Start by using Heatmaps and Session Recordings to visualise the user experience and understand where visitors are hesitating, experiencing points of frustration, and exiting. 

  You need to outline what drives certain patterns in behaviour — like cart abandonment for specific products, and what you think can fix them.

  

  Let’s look at an example. In the screenshot above, we used Matomo’s Heatmap feature to analyse user behaviour on our website. 

  Only 65% of visitors scroll down far enough to encounter our main call to action to “Write a Review.” This insight suggests a potential opportunity for optimisation, where we can focus efforts on encouraging more users to engage with this key element on our site.

  Once you’ve identified an area of improvement, you need to test the results of your proposed solution to the problem. The most common way to do this is with an A/B test. 

  This is a test where you create a new version of the problematic page, trying different titles, comparing long, and short copy, adding or removing images, testing variations of call-to-action buttons and more. Then, you compare the results — the conversion rate — against the original. With Matomo’s A/B Testing feature, you can easily split traffic between the original and one or more variations.

  

  In the example above from Matomo, we can see that testing different header sizes on a page revealed that the wider header led to a higher conversion rate of 47%, compared to the original rate of 35% and the smaller header’s 36%.

  Matomo’s report also analyses the “statistical significance” of the difference in results. Essentially, this is the likelihood that the difference comes from the changes you made in the variation. With a small sample size, random patterns (like one page receiving more organic search visits) can cause the differences.

  If you see a significant change over a larger sample size, you can be fairly certain that the difference is meaningful. And that’s exactly what a high statistical significance rating indicates in Matomo. 

  Once a winner is identified, you can apply the change and start a new experiment. 

  3. Create a culture of data-driven decision-making

  Marketers can no longer afford to rely on guesswork or gamble away budgets and resources. In our digital age, you must use data to get ahead of the competition. In 2021, 65% of business leaders agreed that decisions were getting more complex.

  CRO is a great way to start a company-wide focus on data-driven decision-making. 

  Best practices to start a data-driven culture :
  

  Don’t only test “hunches” or “best practices” — look at the data. Figure out the patterns that highlight how different types of visitors interact with your site.

  Try to answer these questions :

  • How do our most valuable customers interact with our site before purchasing ?
  • How do potential customers who abandon their carts act ?
  • Where do our most valuable customers come from ?

  Moreover, it’s key to democratise insights by providing multiple team members access to information, fostering informed decision-making company-wide.

  4. Lower your acquisition costs and get higher ROI from all marketing efforts

  Once you make meaningful optimisations, CRO can help you lower customer acquisition costs (CAC). Getting new customers through advertising will be cheaper.

  As a result, you’ll get a better return on investment (ROI) on all your campaigns. Every ad and dollar invested will get you closer to a new customer than before. That’s the bottom line of CRO.

  Best practices to lower your CAC (customer acquisition costs) through CRO adjustments :

  The easiest way to lower acquisition costs is to understand where your customers come from. Use marketing attribution to track the results of your campaigns, revealing how each touchpoint contributes to conversions and revenue over time, beyond just last-click attribution.

  You can then compare the number of conversions to the marketing costs of each channel, to get a channel-specific breakdown of CAC.

  This performance overview can help you quickly prioritise the best value channels and ads, lowering your CAC. But these are only surface-level insights. 

  You can also further lower CAC by optimising the pages these campaigns send visitors to. Start with a deep dive into your landing pages using features like Matomo’s Session Recordings or Heatmaps.

  They can help you identify issues with an unengaging user experience or content. Using these insights, you can create A/B tests, where you implement a new page that replaces problematic headlines, buttons, copy, or visuals.

  

  When a test shows a statistically significant improvement in conversion rates, implement the new version. Repeat this over time, and you can increase your conversion rates significantly, getting more customers with the same spend. This will reduce your customer acquisition costs, and help your company grow faster without increasing your ad budget.

  5. Improve your average order value (AOV) and customer lifetime value (CLV)

  CRO isn’t only about increasing the number of customers you convert. If you adapt your approach, you can also use it to increase the revenue from each customer you bring in. 

  But you can’t do that by only tracking conversion rates, you also need to track exactly what your customers buy.

  If you only blindly optimise for CAC, you even risk lowering your CLV and the overall profitability of your campaigns. (For example, if you focus on Facebook Ads with a $6 CAC, but an average CLV of $50, over Google Ads with a $12 CAC, but a $100 CLV.)

  Best practices to track and improve CLV :

  First, integrate your analytics platform with your e-commerce (B2C) or your CRM (B2B). This will help you get a more holistic view of your customers. You don’t want the data to stop at “converted.” You want to be able to dive deep into the patterns of high-value customers.

  The sales report in Matomo’s ecommerce analytics makes it easy to break down average order value by channels, campaigns, and specific ads.

  

  In the report above, we can see that search engines drive customers who spend significantly more, on average, than social networks — $241 vs. $184. But social networks drive a higher volume of customers and more revenue.

  To figure out which channel to focus on, you need to see how the CAC compares to the AOV (or CLV for B2B customers). Let’s say the CAC of social networks is $50, while the search engine CAC is $65. Search engine customers are more profitable — $176 vs. $134. So you may want to adjust some more budget to that channel.

  To put it simply :

  Profit per customer = AOV (or CLV) – CAC

  Example :

  • Profit per customer for social networks = $184 – $50 = $134
  • Profit per customer for search engines = $241 – $65 = $176

  You can also try to A/B test changes that may increase the AOV, like creating a product bundle and recommending it on specific sales pages.

  An improvement in CLV will make your campaigns more profitable, and help stretch your advertising budget even further.

  6. Improve your content and SEO rankings

  A valuable side-effect of focusing on CRO metrics and analyses is that it can boost your SEO rankings. 

  How ? 

  CRO helps you improve the user experience of your website. That’s a key signal Google (and other search engines) care about when ranking webpages. 

  

  For example, Google’s algorithm considers “dwell time,” AKA how long a user stays on your page. If many users quickly return to the results page and click another result, that’s a bad sign. But if most people stay on your site for a while (or don’t return to Google at all), Google thinks your page gives the user their answer.

  As a result, Google will improve your website’s ranking in the search results.

  Best practices to make the most of CRO when it comes to SEO :

  Use A/B Testing, Heatmaps, and Session Recordings to run experiments and understand user behaviour. Test changes to headlines, page layout, imagery and more to see how it impacts the user experience. You can even experiment with completely changing the content on a page, like substituting an introduction.

  Bring your CRO-testing mindset to important pages that aren’t ranking well to improve metrics like dwell time.

  Start optimising your conversion rate today

  As you’ve seen, enjoying the benefits of CRO heavily relies on the data from a reliable web analytics solution. 

  But in an increasingly privacy-conscious world (just look at the timeline of GDPR updates and fines), you must tread carefully. One of the dilemmas that marketing managers face today is whether to prioritise data quality or privacy (and regulations).

  With Matomo, you don’t have to choose. Matomo values both data quality and privacy, adhering to stringent privacy laws like GDPR and CCPA.

  Unlike other web analytics, Matomo doesn’t sample data or use AI and machine learning to fill data gaps. Plus, you can track without annoying visitors with a cookie consent banner – so you capture 100% of traffic while respecting user privacy (excluding in Germany and UK).

  And as you’ve already seen above, you’ll still get plenty of reports and insights to drive your CRO efforts. With User Flows, Funnels, Session Recordings, Form Analytics, and Heatmaps, you can immediately find insights to improve your bottom line.

  And our built-in A/B testing feature will help you test your hypotheses and drive reliable progress. If you’re ready to reliably optimise conversion rates (with accuracy and without privacy concerns), try Matomo for free for 21 days. No credit card required.

  Try Matomo for Free

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• Encoding AV1 to h264 error : Assertion pkt failed at D :/code/ffmpeg/src/fftools/ffmpeg_dec.c:518 [closed]

  1er mars 2024, par KyonGiang

  I used below code to convert from AV1 to x264 mp4, and I got error message : "Assertion pkt failed at D :/code/ffmpeg/src/fftools/ffmpeg_dec.c:518"

  


  ffmpeg -i input.mp4 -c:v h264_nvenc -c:a copy output.mp4 


  


  

  • I'm using Windows 10 64b, Command Prompt, ffmpeg version 2024-01-20-git-6c4388b468-full_build-www.gyan.dev

  


  


  I removed h264_nvenc, Run as Administrator but the result is same.

  


  ffmpeg -i input.mp4 -c:v -c:a copy output.mp4