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• Rotating a video during encoding with ffmpeg and libav API results in half of video corrupted

  11 mai 2020, par Daniel Kobe

  I'm using the C API for ffmpeg/libav to rotate a vertically filmed iphone video during the encoding step. There are other questions asking to do a similar thing but they are all using the CLI tool to do so.

  



  So far I was able to figure out how to use the AVFilter to rotate the video, base off this example https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/filtering_video.c

  



  The problem is that half the output file is corrupt.


  



  Here is the code for my encoding logic. Its written with GOLANG using CGO to interface with the C API.

  



  // Encode encode an AVFrame and return it
func Encode(enc Encoder, frame *C.AVFrame) (*EncodedFrame, error) {
    ctx := enc.Context()

    if ctx.buffersrcctx == nil {
        // initialize filter
        outputs := C.avfilter_inout_alloc()
        inputs  := C.avfilter_inout_alloc()
        m_pFilterGraph := C.avfilter_graph_alloc()
        buffersrc := C.avfilter_get_by_name(C.CString("buffer"))
        argsStr := fmt.Sprintf("video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d", ctx.avctx.width, ctx.avctx.height, ctx.avctx.pix_fmt, ctx.avctx.time_base.num, ctx.avctx.time_base.den, ctx.avctx.sample_aspect_ratio.num, ctx.avctx.sample_aspect_ratio.den)
        Log.Info.Println("yakotest")
        Log.Info.Println(argsStr)
        args := C.CString(argsStr)
        ret := C.avfilter_graph_create_filter(&ctx.buffersrcctx, buffersrc, C.CString("my_buffersrc"), args, nil, m_pFilterGraph)
        if ret < 0 {
            Log.Info.Printf("\n problem creating filter %v\n", AVError(ret).Error())
        }

        buffersink := C.avfilter_get_by_name(C.CString("buffersink"))
        ret = C.avfilter_graph_create_filter(&ctx.buffersinkctx, buffersink, C.CString("my_buffersink"), nil, nil, m_pFilterGraph)
        if ret < 0 {
            Log.Info.Printf("\n problem creating filter %v\n", AVError(ret).Error())
        }

        /*
         * Set the endpoints for the filter graph. The filter_graph will
         * be linked to the graph described by filters_descr.
         */

        /*
         * The buffer source output must be connected to the input pad of
         * the first filter described by filters_descr; since the first
         * filter input label is not specified, it is set to "in" by
         * default.
         */
        outputs.name       = C.av_strdup(C.CString("in"))
        outputs.filter_ctx = ctx.buffersrcctx
        outputs.pad_idx    = 0
        outputs.next       = nil

        /*
         * The buffer sink input must be connected to the output pad of
         * the last filter described by filters_descr; since the last
         * filter output label is not specified, it is set to "out" by
         * default.
         */
        inputs.name       = C.av_strdup(C.CString("out"))
        inputs.filter_ctx = ctx.buffersinkctx
        inputs.pad_idx    = 0
        inputs.next       = nil

        ret = C.avfilter_graph_parse_ptr(m_pFilterGraph, C.CString("transpose=clock,scale=-2:1080"),
            &inputs, &outputs, nil)
        if ret < 0 {
            Log.Info.Printf("\n problem with avfilter_graph_parse %v\n", AVError(ret).Error())
        }

        ret = C.avfilter_graph_config(m_pFilterGraph, nil)
        if ret < 0 {
            Log.Info.Printf("\n problem with graph config %v\n", AVError(ret).Error())
        }
    }

    filteredFrame :=  C.av_frame_alloc()

    /* push the decoded frame into the filtergraph */
    ret := C.av_buffersrc_add_frame_flags(ctx.buffersrcctx, frame, C.AV_BUFFERSRC_FLAG_KEEP_REF)
    if ret < 0 {
        Log.Error.Printf("\nError while feeding the filter greaph, err = %v\n", AVError(ret).Error())
        return nil, errors.New(ErrorFFmpegCodecFailure)
    }

    /* pull filtered frames from the filtergraph */
    for {
        ret = C.av_buffersink_get_frame(ctx.buffersinkctx, filteredFrame)
        if ret == C.AVERROR_EAGAIN || ret == C.AVERROR_EOF {
            break
        }
        if ret < 0 {
            Log.Error.Printf("\nCouldnt find a frame, err = %v\n", AVError(ret).Error())
            return nil, errors.New(ErrorFFmpegCodecFailure)
        }

        filteredFrame.pts = frame.pts
        frame = filteredFrame
        defer C.av_frame_free(&filteredFrame)
    }

    if frame != nil {
        frame.pict_type = 0 // reset pict type for the encoder
        if C.avcodec_send_frame(ctx.avctx, frame) != 0 {
            Log.Error.Printf("%+v\n", StackErrorf("codec error, could not send frame"))
            return nil, errors.New(ErrorFFmpegCodecFailure)
        }
    }

    for {
        ret := C.avcodec_receive_packet(ctx.avctx, ctx.pkt)
        if ret == C.AVERROR_EAGAIN {
            break
        }
        if ret == C.AVERROR_EOF {
            return nil, fmt.Errorf("EOF")
        }
        if ret < 0 {
            Log.Error.Printf("%+v\n", StackErrorf("codec error, receiving packet"))
            return nil, errors.New(ErrorFFmpegCodecFailure)
        }

        data := C.GoBytes(unsafe.Pointer(ctx.pkt.data), ctx.pkt.size)
        return &EncodedFrame{data, int64(ctx.pkt.pts), int64(ctx.pkt.dts),
            (ctx.pkt.flags & C.AV_PKT_FLAG_KEY) != 0}, nil
    }

    return nil, nil
}


  



  It seems like I need to do something with the scaling here but I'm struggling to find helpful information online.

  


• How to make your plugin multilingual – Introducing the Piwik Platform

  29 octobre 2014, par Thomas Steur — Development

  This is the next post of our blog series where we introduce the capabilities of the Piwik platform (our previous post was Generating test data – Introducing the Piwik Platform). This time you’ll learn how to equip your plugin with translations. Users of your plugin will be very thankful that they can use and translate the plugin in their language !

  Getting started

  In this post, we assume that you have already set up your development environment and created a plugin. If not, visit the Piwik Developer Zone where you’ll find the tutorial Setting up Piwik and other Guides that help you to develop a plugin.

  Managing translations

  Piwik is available in over 50 languages and comes with many translations. The core itself provides some basic translations for words like “Visitor” and “Help”. They are stored in the directory /lang. In addition, each plugin can provide its own translations for wordings that are used in this plugin. They are located in /plugins/*/lang. In those directories you’ll find one JSON file for each language. Each language file consists in turn of tokens that belong to a group.

  {
  
      "MyPlugin":{
  
          "BlogPost": "Blog post",
  
          "MyToken": "My translation",
  
          "InteractionRate": "Interaction Rate"
  
      }
  
  }

  A group usually represents the name of a plugin, in this case “MyPlugin”. Within this group, all the tokens are listed on the left side and the related translations on the right side.

  Building a translation key

  As you will later see to actually translate a word or a sentence you’ll need to know the corresponding translation key. This key is built by combining a group and a token separated by an underscore. You can for instance use the key MyPlugin_BlogPost to get a translation of “Blog post”. Defining a new key is as easy as adding a new entry to the “MyPlugin” group.

  Providing default translations

  If a translation cannot be found then the English translation will be used as a default. Therefore, you should always provide a default translation in English for all keys in the file en.json (ie, /plugins/MyPlugin/lang/en.json).

  Adding translations for other languages

  This is as easy as creating new files in the lang subdirectory of your plugin. The filename consists of a 2 letter ISO 639-1 language code completed by the extension .json. This means German translations go into a file named de.json, French ones into a file named fr.json. To see a list of languages you can use have a look at the /lang directory.

  Reusing translations

  As mentioned Piwik comes with quite a lot of translations. You can and should reuse them but you are supposed to be aware that a translation key might be removed or renamed in the future. It is also possible that a translation key was added in a recent version and therefore is not available in older versions of Piwik. We do not currently announce any of such changes. Still, 99% of the translation keys do not change and it is therefore usually a good idea to reuse existing translations. Especially when you or your company would otherwise not be able to provide them. To find any existing translation keys go to Settings => Translation search in your Piwik installation. The menu item will only appear if the development mode is enabled.

  Translations in PHP

  Use the Piwik::translate() function to translate any text in PHP. Simply pass any existing translation key and you will get the translated text in the language of the current user in return. The English translation will be returned in case none for the current language exists.

  $translatedText = Piwik::translate('MyPlugin_BlogPost');

  Translations in Twig Templates

  To translate text in Twig templates, use the translate filter.

  {{ 'MyPlugin_BlogPost'|translate }}

  Contributing translations to Piwik

  Did you know you can contribute translations to Piwik ? In case you want to improve an existing translation, translate a missing one or add a new language go to Piwik Translations and sign up for an account. You won’t need any knowledge in development to do this.

  Advanced features

  Of course there are more useful things you can do with translations. For instance you can use placeholders like %s in your translations and you can use translations in JavaScript as well. In case you want to know more about those topics check out our Internationalization guide. Currently, this guide only covers translations but we will cover more topics like formatting numbers and handling currencies in the future.

  Congratulations, you have learnt how to make your plugin multilingual !

  If you have any feedback regarding our APIs or our guides in the Developer Zone feel free to send it to us.

• How to make your plugin multilingual – Introducing the Piwik Platform

  29 octobre 2014, par Thomas Steur — Development

  This is the next post of our blog series where we introduce the capabilities of the Piwik platform (our previous post was Generating test data – Introducing the Piwik Platform). This time you’ll learn how to equip your plugin with translations. Users of your plugin will be very thankful that they can use and translate the plugin in their language !

  Getting started

  In this post, we assume that you have already set up your development environment and created a plugin. If not, visit the Piwik Developer Zone where you’ll find the tutorial Setting up Piwik and other Guides that help you to develop a plugin.

  Managing translations

  Piwik is available in over 50 languages and comes with many translations. The core itself provides some basic translations for words like “Visitor” and “Help”. They are stored in the directory /lang. In addition, each plugin can provide its own translations for wordings that are used in this plugin. They are located in /plugins/*/lang. In those directories you’ll find one JSON file for each language. Each language file consists in turn of tokens that belong to a group.

  {
  
      "MyPlugin":{
  
          "BlogPost": "Blog post",
  
          "MyToken": "My translation",
  
          "InteractionRate": "Interaction Rate"
  
      }
  
  }

  A group usually represents the name of a plugin, in this case “MyPlugin”. Within this group, all the tokens are listed on the left side and the related translations on the right side.

  Building a translation key

  As you will later see to actually translate a word or a sentence you’ll need to know the corresponding translation key. This key is built by combining a group and a token separated by an underscore. You can for instance use the key MyPlugin_BlogPost to get a translation of “Blog post”. Defining a new key is as easy as adding a new entry to the “MyPlugin” group.

  Providing default translations

  If a translation cannot be found then the English translation will be used as a default. Therefore, you should always provide a default translation in English for all keys in the file en.json (ie, /plugins/MyPlugin/lang/en.json).

  Adding translations for other languages

  This is as easy as creating new files in the lang subdirectory of your plugin. The filename consists of a 2 letter ISO 639-1 language code completed by the extension .json. This means German translations go into a file named de.json, French ones into a file named fr.json. To see a list of languages you can use have a look at the /lang directory.

  Reusing translations

  As mentioned Piwik comes with quite a lot of translations. You can and should reuse them but you are supposed to be aware that a translation key might be removed or renamed in the future. It is also possible that a translation key was added in a recent version and therefore is not available in older versions of Piwik. We do not currently announce any of such changes. Still, 99% of the translation keys do not change and it is therefore usually a good idea to reuse existing translations. Especially when you or your company would otherwise not be able to provide them. To find any existing translation keys go to Settings => Translation search in your Piwik installation. The menu item will only appear if the development mode is enabled.

  Translations in PHP

  Use the Piwik::translate() function to translate any text in PHP. Simply pass any existing translation key and you will get the translated text in the language of the current user in return. The English translation will be returned in case none for the current language exists.

  $translatedText = Piwik::translate('MyPlugin_BlogPost');

  Translations in Twig Templates

  To translate text in Twig templates, use the translate filter.

  {{ 'MyPlugin_BlogPost'|translate }}

  Contributing translations to Piwik

  Did you know you can contribute translations to Piwik ? In case you want to improve an existing translation, translate a missing one or add a new language go to Piwik Translations and sign up for an account. You won’t need any knowledge in development to do this.

  Advanced features

  Of course there are more useful things you can do with translations. For instance you can use placeholders like %s in your translations and you can use translations in JavaScript as well. In case you want to know more about those topics check out our Internationalization guide. Currently, this guide only covers translations but we will cover more topics like formatting numbers and handling currencies in the future.

  Congratulations, you have learnt how to make your plugin multilingual !

  If you have any feedback regarding our APIs or our guides in the Developer Zone feel free to send it to us.