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• Open stream with FFmpeg libavformat exits with I/O error after once in Android Application

  15 février 2015, par miazima

  I am trying to open a video stream in an android application. The first time I open the stream, the stream is opened and everything runs fine. However, if I press back and open the stream again, the app crashes.

  I am a newbie to this, so I used log statements to see if the argument values for the methods could lead me to the issue. I figured out that avformat_open_input(&ic, is->filename, is->iformat, NULL) is returning I/O error. However I can’t figure out where the error lies, the filename and the format is the same but am not sure about the &ic which is from is->ic = (AVFormatContext*) avformat_alloc_context(), I would appreciate any help !

  void get_video_info(int p_debug, const char* path) {
  
  
  
      int flags;
  
      //VideoState *is;
  
      int err, i, orig_nb_streams, ret;
  
      isquit = 0;
  
      av_log_set_flags(AV_LOG_SKIP_REPEATED);
  
      int st_index[3];
  
      st_index[AVMEDIA_TYPE_AUDIO]=-1;
  
      st_index[AVMEDIA_TYPE_VIDEO]=-1;
  
      /* register all codecs, demux and protocols */
  
      avcodec_register_all();
  
  #if CONFIG_AVDEVICE
  
      avdevice_register_all();
  
  #endif
  
  #if CONFIG_AVFILTER
  
      avfilter_register_all();
  
  #endif
  
      av_register_all();
  
  #if CONFIG_NETWORK
  
      ret = avformat_network_init();
  
  #endif
  
       if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
  
              fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
  
              exit(1);
  
            }
  
  
  
      av_init_packet(&flush_pkt);
  
      flush_pkt.data = "FLUSH";
  
  
  
      // open video stream
  
      is = av_mallocz(sizeof(VideoState));
  
      if (!is) {
  
          do_exit(NULL);
  
          return;
  
      }
  
  
  
      is->abort_request = 0; // FIXME: abort_request changes when on closing or exit
  
      is->pictq_mutex = SDL_CreateMutex();
  
      is->pictq_cond = SDL_CreateCond();
  
      is->pictq_size = 0;
  
      is->pictq_rindex = 0;
  
      is->pictq_windex = 0;
  
      is->av_sync_type = av_sync_type;//AV_SYNC_AUDIO_MASTER;//
  
  
  
      if(path != NULL)
  
      {
  
          av_strlcpy(is->filename, path, sizeof(is->filename));
  
      }
  
      else
  
      {
  
          if(streamProtocal==0) {
  
              av_strlcpy(is->filename, "/sdcard/download/sdp_file.sdp", sizeof(is->filename));
  
          }
  
          else
  
          {
  
              av_strlcpy(is->filename, "udp://@:3001", sizeof(is->filename));
  
              is->iformat = av_find_input_format("m4v");
  
          }
  
      }
  
      is->ic = (AVFormatContext*) avformat_alloc_context();
  
      //It is assumed that server always sends m4v data, so that codec search can be avoided
  
      AVFormatContext *ic = is->ic;
  
  
  
      if ((err = avformat_open_input(&ic, is->filename, is->iformat, NULL))
  
              != 0) {
  
          LOGE(1, "Error open video file: %s", is->filename);
  
          char* error = (char*)malloc(1024);
  
          av_strerror(err, error, 1024);
  
          LOGE(1, "Error open video file: %s", error);
  
          do_exit(is);
  
      }
  
      LOGE(1, "entered get_video_info");
  
      is->ic = ic;
  
  
  
      orig_nb_streams = ic->nb_streams;
  
      if ((err = avformat_find_stream_info(is->ic, NULL)) < 0) {
  
          LOGE(1, "Error find stream information: %d", err);
  
          return;
  
      }
  
      LOGE(1, "avformat_find_stream_info");
  
      if(is->ic->pb)
  
          is->ic->pb->eof_reached= 0;//FIXME hack, ffplay maybe should not use url_feof() to test for the end
  
      AVCodec *lvideoCodec;
  
  
  
  int g_audio_file_type = 0;
  
      // Find the first video stream
  
          for (i=0; iic->nb_streams; i++) {
  
              //take video stream only for video file types
  
              if (g_audio_file_type == 0)  {
  
                  if (is->ic->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO &&
  
                          st_index[AVMEDIA_TYPE_VIDEO] < 0)
  
                  {
  
                      st_index[AVMEDIA_TYPE_VIDEO]=i;
  
                  }
  
              }
  
  
  
              if(is->ic->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO &&
  
                      st_index[AVMEDIA_TYPE_AUDIO] < 0)
  
              {
  
                  st_index[AVMEDIA_TYPE_AUDIO]=i;
  
              }
  
  
  
          }
  
      if (st_index[AVMEDIA_TYPE_AUDIO] >= 0) {
  
          stream_component_open(is, st_index[AVMEDIA_TYPE_AUDIO]);
  
      }
  
      if (st_index[AVMEDIA_TYPE_VIDEO] >= 0) {
  
          stream_component_open(is, st_index[AVMEDIA_TYPE_VIDEO]);
  
      }
  
      if (is->video_stream < 0) {
  
          do_exit(is);
  
          return;
  
      }
  
      is->read_tid = SDL_CreateThread(read_thread, is);
  
      rgb_frame = avcodec_alloc_frame();
  
  }

• Benefits and Shortcomings of Multi-Touch Attribution

  13 mars 2023, par Erin — Analytics Tips

  Few sales happen instantly. Consumers take their time to discover, evaluate and become convinced to go with your offer. 

  Multi-channel attribution (also known as multi-touch attribution or MTA) helps businesses better understand which marketing tactics impact consumers’ decisions at different stages of their buying journey. Then double down on what’s working to secure more sales. 

  Unlike standard analytics, multi-channel modelling combines data from various channels to determine their cumulative and independent impact on your conversion rates. 

  The main benefit of multi-touch attribution is obvious : See top-performing channels, as well as those involved in assisted conversions. The drawback of multi-touch attribution : It comes with a more complex setup process. 

  If you’re on the fence about getting started with multi-touch attribution, here’s a summary of the main arguments for and against it. 

  What Are the Benefits of Multi-Touch Attribution ?

  Remember an old parable of blind men and an elephant ?

  Each one touched the elephant and drew conclusions about how it might look. The group ended up with different perceptions of the animal and thought the others were lying…until they decided to work together on establishing the truth.

  Multi-channel analytics works in a similar way : It reconciles data from various channels and campaign types into one complete picture. So that you can get aligned on the efficacy of different campaign types and gain some other benefits too. 

  Better Understanding of Customer Journeys 

  On average, it takes 8 interactions with a prospect to generate a conversion. These interactions happen in three stages : 

  • Awareness : You need to introduce your company to the target buyers and pique their interest in your solution (top-of-the-funnel). 
  • Consideration : The next step is to channel this casual interest into deliberate research and evaluation of your offer (middle-of-the-funnel). 
  • Decision : Finally, you need to get the buyer to commit to your offer and close the deal (bottom-of-the-funnel). 

  You can analyse funnels using various attribution models — last-click, fist-click, position-based attribution, etc. Each model, however, will spotlight the different element(s) of your sales funnel. 

  For example, a single-touch attribution model like last-click zooms in on the bottom-of-the-funnel stage. You can evaluate which channels (or on-site elements) sealed the deal for the prospect. For example, a site visitor arrived from an affiliate link and started a free trial. In this case, the affiliate (referral traffic) gets 100% credit for the conversion. 

  This measurement tactic, however, doesn’t show which channels brought the customer to the very bottom of your funnel. For instance, they may have interacted with a social media post, your landing pages or a banner ad before that. 

  Multi-touch attribution modelling takes funnel analysis a notch further. In this case, you map more steps in the customer journey — actions, events, and pages that triggered a visitor’s decision to convert — in your website analytics tool.

  

  Then, select a multi-touch attribution model, which provides more backward visibility aka allows you to track more than one channel, preceding the conversion. 

  For example, a Position Based attribution model reports back on all interactions a site visitor had between their first visit and conversion. 

  A prospect first lands at your website via search results (Search traffic), which gets a 40% credit in this model. Two days later, the same person discovers a mention of your website on another blog and visits again (Referral traffic). This time, they save the page as a bookmark and revisit it again in two more days (Direct traffic). Each of these channels will get a 10% credit. A week later, the prospect lands again on your site via Twitter (Social) and makes a request for a demo. Social would then receive a 40% credit for this conversion. Last-click would have only credited social media and first-click — search engines. 

  The bottom line : Multi-channel attribution models show how different channels (and marketing tactics) contribute to conversions at different stages of the customer journey. Without it, you get an incomplete picture.

  Improved Budget Allocation 

  Understanding causal relationships between marketing activities and conversion rates can help you optimise your budgets.

  First-click/last-click attribution models emphasise the role of one channel. This can prompt you toward the wrong conclusions. 

  For instance, your Facebook ads campaigns do great according to a first-touch model. So you decide to increase the budget. What you might be missing though is that you could have an even higher conversion rate and revenue if you fix “funnel leaks” — address high drop-off rates during checkout, improve page layout and address other possible reasons for exiting the page.

  

  By knowing when and why people abandon their purchase journey, you can improve your marketing velocity (aka the speed of seeing the campaign results) and your marketing costs (aka the budgets you allocate toward different assets, touchpoints and campaign types). 

  Or as one of the godfathers of marketing technology, Dan McGaw, explained in a webinar :

  “Once you have a multi-touch attribution model, you [can] actually know the return on ad spend on a per-campaign basis. Sometimes, you can get it down to keywords. Sometimes, you can get down to all kinds of other information, but you start to realise, “Oh, this campaign sucks. I should shut this off.” And then really, that’s what it’s about. It’s seeing those campaigns that suck and turning them off and then taking that budget and putting it into the campaigns that are working”.

  More Accurate Measurements 

  The big boon of multi-channel marketing attribution is that you can zoom in on various elements of your funnel and gain granular data on the asset’s performance. 

  In other words : You get more accurate insights into the different elements involved in customer journeys. But for accurate analytics measurements, you must configure accurate tracking. 

  Define your objectives first : How do you want a multi-touch attribution tool to help you ? Multi-channel attribution analysis helps you answer important questions such as :

  • How many touchpoints are involved in the conversions ? 
  • How long does it take for a lead to convert on average ? 
  • When and where do different audience groups convert ? 
  • What is your average win rate for different types of campaigns ?

  Your objectives will dictate which multi-channel modelling approach will work best for your business — as well as the data you’ll need to collect. 

  At the highest level, you need to collect two data points :

  • Conversions : Desired actions from your prospects — a sale, a newsletter subscription, a form submission, etc. Record them as tracked Goals. 
  • Touchpoints : Specific interactions between your brand and targets — specific page visits, referral traffic from a particular marketing channel, etc. Record them as tracked Events. 

  Your attribution modelling software will then establish correlation patterns between actions (conversions) and assets (touchpoints), which triggered them. 

  The accuracy of these measurements, however, will depend on the quality of data and the type of attribution modelling used. 

  Data quality stands for your ability to procure accurate, complete and comprehensive information from various touchpoints. For instance, some data won’t be available if the user rejected a cookie consent banner (unless you’re using a privacy-focused web analytics tool like Matomo). 

  Different attribution modelling techniques come with inherent shortcomings too as they don’t accurately represent the average sales cycle length or track visitor-level data, which allows you to understand which customer segments convert best.

  Learn more about selecting the optimal multi-channel attribution model for your business.

  What Are the Limitations of Multi-Touch Attribution ?

  Overall, multi-touch attribution offers a more comprehensive view of the conversion paths. However, each attribution model (except for custom ones) comes with inherent assumptions about the contribution of different channels (e.g,. 25%-25%-25%-25% in linear attribution or 40%-10%-10%-40% in position-based attribution). These conversion credit allocations may not accurately represent the realities of your industry. 

  Also, most attribution models don’t reflect incremental revenue you gain from existing customers, which aren’t converting through analysed channels. For example, account upgrades to a higher tier, triggered via an in-app offer. Or warranty upsell, made via a marketing email. 

  In addition, you should keep in mind several other limitations of multi-touch attribution software.

  Limited Marketing Mix Analysis 

  Multi-touch attribution tools work in conjunction with your website analytics app (as they draw most data from it). Because of that, such models inherit the same visibility into your marketing mix — a combo of tactics you use to influence consumer decisions.

  Multi-touch attribution tools cannot evaluate the impact of :

  • Dark social channels 
  • Word-of-mouth 
  • Offline promotional events
  • TV or out-of-home ad campaigns 

  If you want to incorporate this data into your multi-attribution reporting, you’ll have to procure extra data from other systems — CRM, ad measurement partners, etc, — and create complex custom analytics models for its evaluation.

  Time-Based Constraints 

  Most analytics apps provide a maximum 90-day lookback window for attribution. This can be short for companies with longer sales cycles. 

  

  Marketing channels can be overlooked or underappreciated when your attribution window is too short. Because of that, you may curtail spending on brand awareness campaigns, which, in turn, will reduce the number of people entering the later stages of your funnel. 

  At the same time, many businesses would also want to track a look-forward window — the revenue you’ll get from one customer over their lifetime. In this case, not all tools may allow you to capture accurate information on repeat conversions — through re-purchases, account tier updates, add-ons, upsells, etc. 

  Again, to get an accurate picture you’ll need to understand how far into the future you should track conversions. Will you only record your first sales as a revenue number or monitor customer lifetime value (CLV) over 3, 6 or 12 months ? 

  The latter is more challenging to do. But CLV data can add another depth of dimension to your modelling accuracy. With Matomo, you set up this type of tracking by using our visitors’ tracking feature. We can help you track select visitors with known identifiers (e.g. name or email address) to discover their visiting patterns over time. 

  

  Limited Access to Raw Data 

  In web analytics, raw data stands for unprocessed website visitor information, stripped from any filters, segmentation or sampling applied. 

  Data sampling is a practice of analysing data subsets (instead of complete records) to extrapolate findings towards the entire data set. Google Analytics 4 applies data sampling once you hit over 500k sessions at the property level. So instead of accurate, real-life reporting, you receive approximations, generated by machine learning models. Data sampling is one of the main reasons behind Google Analytics’ accuracy issues. 

  In multi-channel attribution modelling, usage of sampled data creates further inconsistencies between the reports and the actual state of affairs. For instance, if your website generates 5 million page views, GA multi-touch analytical reports are based on the 500K sample size aka only 90% of the collected information. This hardly represents the real effect of all marketing channels and can lead to subpar decision-making. 

  With Matomo, the above is never an issue. We don’t apply data sampling to any websites (no matter the volume of traffic) and generate all the reports, including multi-channel attribution ones, based on 100% real user data. 

  AI Application 

  On the other hand, websites with smaller traffic volumes often have limited sampling datasets for building attribution models. Some tracking data may also be not available because the visitor rejected a cookie banner, for instance. On average, less than 50% of users in Australia, France, Germany, Denmark and the US among other countries always consent to all cookies. 

  To compensate for such scenarios, some multi-touch attribution solutions apply AI algorithms to “fill in the blanks”, which impacts the reporting accuracy. Once again, you get approximate data of what probably happened. However, Matomo is legally exempt from showing a cookie consent banner in most EU markets. Meaning you can collect 100% accurate data to make data-driven decisions.

  Difficult Technical Implementation 

  Ever since attribution modelling got traction in digital marketing, more and more tools started to emerge.

  

  Most web analytics apps include multi-touch attribution reports. Then there are standalone multi-channel attribution platforms, offering extra features for conversion rate optimization, offline channel tracking, data-driven custom modelling, etc. 

  Most advanced solutions aren’t available out of the box. Instead, you have to install several applications, configure integrations with requested data sources, and then use the provided interfaces to code together custom data models. Such solutions are great if you have a technical marketer or a data science team. But a steep learning curve and high setup costs make them less attractive for smaller teams. 

  Conclusion 

  Multi-touch attribution modelling lifts the curtain in more steps, involved in various customer journeys. By understanding which touchpoints contribute to conversions, you can better plan your campaign types and budget allocations. 

  That said, to benefit from multi-touch attribution modelling, marketers also need to do the preliminary work : Determine the key goals, set up event and conversion tracking, and then — select the optimal attribution model type and tool. 

  Matomo combines simplicity with sophistication. We provide marketers with familiar, intuitive interfaces for setting up conversion tracking across the funnel. Then generate attribution reports, based on 100% accurate data (without any sampling or “guesstimation” applied). You can also get access to raw analytics data to create custom attribution models or plug it into another tool ! 

  Start using accurate, easy-to-use multi-channel attribution with Matomo. Start your free 21-day trial now. No credit card requried. 

• ffmdec : limit the backward seek to the last resync position

  9 mars 2015, par Andreas Cadhalpun

  ffmdec : limit the backward seek to the last resync position
  If resyncing leads to the same position as previously, it will again
  
  lead to a resync attempt, resulting in an infinite loop.
  Thus don’t seek back beyond the last syncpoint.
  Signed-off-by : Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavformat/ffmdec.c