{"id":94138,"date":"2020-09-13T07:42:42","date_gmt":"2020-09-13T05:42:42","guid":{"rendered":"https:\/\/prohoster.info\/blog\/administrirovanie\/pochti-bespoleznyj-striming-vebkamery-iz-brauzera-media-stream-i-websockets"},"modified":"2020-09-13T07:42:42","modified_gmt":"2020-09-13T05:42:42","slug":"pochti-bespoleznyj-striming-vebkamery-iz-brauzera-media-stream-i-websockets","status":"publish","type":"post","link":"https:\/\/prohoster.info\/it\/blog\/administrirovanie\/pochti-bespoleznyj-striming-vebkamery-iz-brauzera-media-stream-i-websockets","title":{"rendered":"(Quasi) streaming inutile della webcam dal browser. Media Stream e Websockets","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

In questo articolo voglio condividere i miei tentativi di fare streaming video tramite websocket senza utilizzare plugin esterni per il browser come Adobe Flash Player. Leggi oltre per scoprire cosa \u00e8 venuto fuori.
\n<\/a><\/noindex>
\nAdobe Flash \u2014 precedentemente Macromedia Flash, \u00e8 una piattaforma per la creazione di applicazioni che funzionano nei browser web. Prima dell'introduzione dell'API Media Stream, era praticamente l'unica piattaforma per lo streaming di video e audio dalla webcam, oltre che per creare vari tipi di conferenze e chat nel browser. Il protocollo per la trasmissione di informazioni multimediali, RTMP (Real Time Messaging Protocol), \u00e8 stato praticamente chiuso per lungo tempo, il che significava: se vuoi avviare il tuo servizio di streaming, devi usare il software di Adobe stesso \u2014 Adobe Media Server (AMS). <\/p>\n

Dopo un po', nel 2012, Adobe si \u00e8 'arresa e ha sputato' davanti al pubblico specifica<\/a><\/noindex> del protocollo RTMP, che conteneva errori e in realt\u00e0 era incompleta. A quel tempo, gli sviluppatori avevano iniziato a realizzare le loro implementazioni di questo protocollo, ed \u00e8 cos\u00ec che \u00e8 nato il server Wowza. Nel 2011 Adobe ha fatto causa a Wowza per uso illegale di brevetti relativi a RTMP, e dopo 4 anni il conflitto \u00e8 stato risolto pacificamente. <\/p>\n

La piattaforma Adobe Flash ha pi\u00f9 di 20 anni, durante i quali sono emerse molte vulnerabilit\u00e0 critiche, il supporto era previsto<\/a><\/noindex> di cessare nel 2020, quindi le alternative per il servizio di streaming non sono poi cos\u00ec molte. <\/p>\n

Per il mio progetto, ho deciso fin da subito di rinunciare completamente all'uso di Flash nel browser. La ragione principale l'ho indicata sopra, inoltre Flash non \u00e8 affatto supportato sulle piattaforme mobili, e nemmeno avevo voglia di avviare Adobe Flash per lo sviluppo su Windows (emulatore wine). Quindi ho iniziato a scrivere un client in JavaScript. Sar\u00e0 solo un prototipo, poich\u00e9 successivamente ho scoperto che lo streaming pu\u00f2 essere fatto in modo molto pi\u00f9 efficiente sulla base di p2p, solo che nel mio caso sar\u00e0 peer \u2014 server \u2014 peers, ma di questo parleremo un'altra volta, perch\u00e9 non \u00e8 ancora pronto.<\/p>\n

Per iniziare, abbiamo bisogno fondamentalmente di un server websocket. Ho realizzato il pi\u00f9 semplice basato sul pacchetto go melody:<\/p>\n

Codice della parte server<\/b><\/p>\n

package main\n\nimport (\n\t\"errors\"\n\t\"github.com\/go-chi\/chi\"\n\t\"gopkg.in\/olahol\/melody.v1\"\n\t\"log\"\n\t\"net\/http\"\n\t\"time\"\n)\n\nfunc main() {\n\tr := chi.NewRouter()\n\tm := melody.New()\n\n\tm.Config.MaxMessageSize = 204800\n\n\tr.Get(\"\/\", func(w http.ResponseWriter, r *http.Request) {\n\t\thttp.ServeFile(w, r, \"public\/index.html\")\n\t})\n\tr.Get(\"\/ws\", func(w http.ResponseWriter, r *http.Request) {\n\t\tm.HandleRequest(w, r)\n\t})\n\n         \/\/ Trasmettiamo il flusso video \n\tm.HandleMessageBinary(func(s *melody.Session, msg []byte) {\n\t\tm.BroadcastBinary(msg)\n\t})\n\n\tlog.Println(\"Avvio del server...\")\n\n\thttp.ListenAndServe(\":3000\", r)\n}\n<\/code><\/pre>\n
Sul client (lato trasmittente) \u00e8 necessario prima ottenere l'accesso alla videocamera. Questo avviene tramite API MediaStream<\/a><\/noindex>.<\/p>\n
Otteniamo l'accesso (autorizzazione) alla videocamera\/microfono tramite Media Devices API<\/a><\/noindex>. Questa API fornisce il metodo MediaDevices.getUserMedia()<\/a><\/noindex>, che mostra un popup che chiede all'utente l'autorizzazione per accedere alla videocamera o\/ai microfoni. \u00c8 importante notare che ho effettuato tutti gli esperimenti su Google Chrome, ma credo che su Firefox funzioni in modo simile.<\/p>\n
Successivamente, getUserMedia() restituisce una Promise che trasmette un oggetto MediaStream \u2014 un flusso di dati video-audio. Questo oggetto lo assegniamo alla propriet\u00e0 src dell'elemento video. Codice:<\/p>\n
                        Lato trasmittente<\/b><\/p>\n
<style>\n  #videoObjectHtml5ApiServer { width: 320px; height: 240px; background: #666; }\n<\/style>\n<\/head>\n<body>\n<!-- \u0417\u0434\u0435\u0441\u044c \u0432 \u044d\u0442\u043e\u043c "\u043e\u043a\u043e\u0448\u0435\u0447\u043a\u0435" \u043a\u043b\u0438\u0435\u043d\u0442 \u0431\u0443\u0434\u0435\u0442 \u0432\u0438\u0434\u0435\u0442\u044c \u0441\u0435\u0431\u044f -->\n<video autoplay id="videoObjectHtml5ApiServer"><\/video>\n\n<script type="application\/javascript">\n  var\n        video = document.getElementById('videoObjectHtml5ApiServer');\n\n\/\/ \u0435\u0441\u043b\u0438 \u0434\u043e\u0441\u0442\u0443\u043f\u0435\u043d MediaDevices API, \u043f\u044b\u0442\u0430\u0435\u043c\u0441\u044f \u043f\u043e\u043b\u0443\u0447\u0438\u0442\u044c \u0434\u043e\u0441\u0442\u0443\u043f \u043a \u043a\u0430\u043c\u0435\u0440\u0435 (\u043c\u043e\u0436\u043d\u043e \u0435\u0449\u0435 \u0438 \u043a \u043c\u0438\u043a\u0440\u043e\u0444\u043e\u043d\u0443)\n\/\/ getUserMedia \u0432\u0435\u0440\u043d\u0435\u0442 \u043e\u0431\u0435\u0449\u0430\u043d\u0438\u0435, \u043d\u0430 \u043a\u043e\u0442\u043e\u0440\u043e\u0435 \u043f\u043e\u0434\u043f\u0438\u0441\u044b\u0432\u0430\u0435\u043c\u0441\u044f \u0438 \u043f\u043e\u043b\u0443\u0447\u0435\u043d\u043d\u044b\u0439 \u0432\u0438\u0434\u0435\u043e\u043f\u043e\u0442\u043e\u043a \u0432 \u043a\u043e\u043b\u0431\u0435\u043a\u0435 \u043d\u0430\u043f\u0440\u0430\u0432\u043b\u044f\u0435\u043c \u0432 video \u043e\u0431\u044a\u0435\u043a\u0442 \u043d\u0430 \u0441\u0442\u0440\u0430\u043d\u0438\u0446\u0435\n\nif (navigator.mediaDevices.getUserMedia) {\n        navigator.mediaDevices.getUserMedia({video: true}).then(function (stream) {\n          \/\/ \u0432\u0438\u0434\u0435\u043e \u043f\u043e\u0442\u043e\u043a \u043f\u0440\u0438\u0432\u044f\u0437\u044b\u0432\u0430\u0435\u043c \u043a video \u0442\u0435\u0433\u0443, \u0447\u0442\u043e\u0431\u044b \u043a\u043b\u0438\u0435\u043d\u0442 \u043c\u043e\u0433 \u0432\u0438\u0434\u0435\u0442\u044c \u0441\u0435\u0431\u044f \u0438 \u043a\u043e\u043d\u0442\u0440\u043e\u043b\u0438\u0440\u043e\u0432\u0430\u0442\u044c \n          video.srcObject = stream;\n        });\n}\n<\/script>\n<\/code><\/pre>\n
Per trasmettere un flusso video attraverso le socket, \u00e8 necessario codificarlo in qualche modo, bufferizzarlo e inviarlo a pezzi. Un flusso video grezzo non pu\u00f2 essere inviato tramite websockets. Qui ci aiuta MediaRecorder API<\/a><\/noindex>. Questa API consente di codificare e suddividere il flusso in pezzi. Codifico per comprimere il flusso video, cos\u00ec da inviare meno byte attraverso la rete. Suddividendo in pezzi, possiamo inviare ogni pezzo via websocket. Codice:<\/p>\n
                        Codifichiamo il flusso video, lo suddividiamo in parti<\/b><\/p>\n
<style>\n  #videoObjectHtml5ApiServer { width: 320px; height: 240px; background: #666; }\n<\/style>\n<\/head>\n<body>\n<!-- \u0417\u0434\u0435\u0441\u044c \u0432 \u044d\u0442\u043e\u043c "\u043e\u043a\u043e\u0448\u0435\u0447\u043a\u0435" \u043a\u043b\u0438\u0435\u043d\u0442 \u0431\u0443\u0434\u0435\u0442 \u0432\u0438\u0434\u0435\u0442\u044c \u0441\u0435\u0431\u044f -->\n<video autoplay id="videoObjectHtml5ApiServer"><\/video>\n\n<script type="application\/javascript">\n  var\n        video = document.getElementById('videoObjectHtml5ApiServer');\n\n\/\/ \u0435\u0441\u043b\u0438 \u0434\u043e\u0441\u0442\u0443\u043f\u0435\u043d MediaDevices API, \u043f\u044b\u0442\u0430\u0435\u043c\u0441\u044f \u043f\u043e\u043b\u0443\u0447\u0438\u0442\u044c \u0434\u043e\u0441\u0442\u0443\u043f \u043a \u043a\u0430\u043c\u0435\u0440\u0435 (\u043c\u043e\u0436\u043d\u043e \u0435\u0449\u0435 \u0438 \u043a \u043c\u0438\u043a\u0440\u043e\u0444\u043e\u043d\u0443)\n\/\/ getUserMedia \u0432\u0435\u0440\u043d\u0435\u0442 \u043e\u0431\u0435\u0449\u0430\u043d\u0438\u0435, \u043d\u0430 \u043a\u043e\u0442\u043e\u0440\u043e\u0435 \u043f\u043e\u0434\u043f\u0438\u0441\u044b\u0432\u0430\u0435\u043c\u0441\u044f \u0438 \u043f\u043e\u043b\u0443\u0447\u0435\u043d\u043d\u044b\u0439 \u0432\u0438\u0434\u0435\u043e\u043f\u043e\u0442\u043e\u043a \u0432 \u043a\u043e\u043b\u0431\u0435\u043a\u0435 \u043d\u0430\u043f\u0440\u0430\u0432\u043b\u044f\u0435\u043c \u0432 video \u043e\u0431\u044a\u0435\u043a\u0442 \u043d\u0430 \u0441\u0442\u0440\u0430\u043d\u0438\u0446\u0435\n\nif (navigator.mediaDevices.getUserMedia) {\n        navigator.mediaDevices.getUserMedia({video: true}).then(function (stream) {\n          \/\/ \u0432\u0438\u0434\u0435\u043e \u043f\u043e\u0442\u043e\u043a \u043f\u0440\u0438\u0432\u044f\u0437\u044b\u0432\u0430\u0435\u043c \u043a video \u0442\u0435\u0433\u0443, \u0447\u0442\u043e\u0431\u044b \u043a\u043b\u0438\u0435\u043d\u0442 \u043c\u043e\u0433 \u0432\u0438\u0434\u0435\u0442\u044c \u0441\u0435\u0431\u044f \u0438 \u043a\u043e\u043d\u0442\u0440\u043e\u043b\u0438\u0440\u043e\u0432\u0430\u0442\u044c \n          video.srcObject = s;\n          var\n            recorderOptions = {\n                mimeType: 'video\/webm; codecs=vp8' \/\/ \u0431\u0443\u0434\u0435\u043c \u043a\u043e\u0434\u0438\u0440\u043e\u0432\u0430\u0442\u044c \u0432\u0438\u0434\u0435\u043e\u043f\u043e\u0442\u043e\u043a \u0432 \u0444\u043e\u0440\u043c\u0430\u0442 webm \u043a\u043e\u0434\u0435\u043a\u043e\u043c vp8\n              },\n              mediaRecorder = new MediaRecorder(s, recorderOptions ); \/\/ \u043e\u0431\u044a\u0435\u043a\u0442 MediaRecorder\n\n               mediaRecorder.ondataavailable = function(e) {\n                if (e.data && e.data.size > 0) {\n                  \/\/ \u043f\u043e\u043b\u0443\u0447\u0430\u0435\u043c \u043a\u0443\u0441\u043e\u0447\u0435\u043a \u0432\u0438\u0434\u0435\u043e\u043f\u043e\u0442\u043e\u043a\u0430 \u0432 e.data\n                }\n            }\n\n            mediaRecorder.start(100); \/\/ \u0434\u0435\u043b\u0438\u0442 \u043f\u043e\u0442\u043e\u043a \u043d\u0430 \u043a\u0443\u0441\u043e\u0447\u043a\u0438 \u043f\u043e 100 \u043c\u0441 \u043a\u0430\u0436\u0434\u044b\u0439\n\n        });\n}\n<\/script>\n<\/code><\/pre>\n
Ora aggiungiamo la trasmissione tramite websockets. Stranamente, per questo basta un oggetto WebSocket<\/a><\/noindex>. Ha solo due metodi: send e close. I nomi parlano da soli. Codice aggiornato:<\/p>\n
                        Inviare il flusso video al server<\/b><\/p>\n
<style>\n  #videoObjectHtml5ApiServer { width: 320px; height: 240px; background: #666; }\n<\/style>\n<\/head>\n<body>\n<!-- \u0417\u0434\u0435\u0441\u044c \u0432 \u044d\u0442\u043e\u043c "\u043e\u043a\u043e\u0448\u0435\u0447\u043a\u0435" \u043a\u043b\u0438\u0435\u043d\u0442 \u0431\u0443\u0434\u0435\u0442 \u0432\u0438\u0434\u0435\u0442\u044c \u0441\u0435\u0431\u044f -->\n<video autoplay id="videoObjectHtml5ApiServer"><\/video>\n\n<script type="application\/javascript">\n  var\n        video = document.getElementById('videoObjectHtml5ApiServer');\n\n\/\/ \u0435\u0441\u043b\u0438 \u0434\u043e\u0441\u0442\u0443\u043f\u0435\u043d MediaDevices API, \u043f\u044b\u0442\u0430\u0435\u043c\u0441\u044f \u043f\u043e\u043b\u0443\u0447\u0438\u0442\u044c \u0434\u043e\u0441\u0442\u0443\u043f \u043a \u043a\u0430\u043c\u0435\u0440\u0435 (\u043c\u043e\u0436\u043d\u043e \u0435\u0449\u0435 \u0438 \u043a \u043c\u0438\u043a\u0440\u043e\u0444\u043e\u043d\u0443)\n\/\/ getUserMedia \u0432\u0435\u0440\u043d\u0435\u0442 \u043e\u0431\u0435\u0449\u0430\u043d\u0438\u0435, \u043d\u0430 \u043a\u043e\u0442\u043e\u0440\u043e\u0435 \u043f\u043e\u0434\u043f\u0438\u0441\u044b\u0432\u0430\u0435\u043c\u0441\u044f \u0438 \u043f\u043e\u043b\u0443\u0447\u0435\u043d\u043d\u044b\u0439 \u0432\u0438\u0434\u0435\u043e\u043f\u043e\u0442\u043e\u043a \u0432 \u043a\u043e\u043b\u0431\u0435\u043a\u0435 \u043d\u0430\u043f\u0440\u0430\u0432\u043b\u044f\u0435\u043c \u0432 video \u043e\u0431\u044a\u0435\u043a\u0442 \u043d\u0430 \u0441\u0442\u0440\u0430\u043d\u0438\u0446\u0435\n\nif (navigator.mediaDevices.getUserMedia) {\n        navigator.mediaDevices.getUserMedia({video: true}).then(function (stream) {\n          \/\/ \u0432\u0438\u0434\u0435\u043e \u043f\u043e\u0442\u043e\u043a \u043f\u0440\u0438\u0432\u044f\u0437\u044b\u0432\u0430\u0435\u043c \u043a video \u0442\u0435\u0433\u0443, \u0447\u0442\u043e\u0431\u044b \u043a\u043b\u0438\u0435\u043d\u0442 \u043c\u043e\u0433 \u0432\u0438\u0434\u0435\u0442\u044c \u0441\u0435\u0431\u044f \u0438 \u043a\u043e\u043d\u0442\u0440\u043e\u043b\u0438\u0440\u043e\u0432\u0430\u0442\u044c \n          video.srcObject = s;\n          var\n            recorderOptions = {\n                mimeType: 'video\/webm; codecs=vp8' \/\/ \u0431\u0443\u0434\u0435\u043c \u043a\u043e\u0434\u0438\u0440\u043e\u0432\u0430\u0442\u044c \u0432\u0438\u0434\u0435\u043e\u043f\u043e\u0442\u043e\u043a \u0432 \u0444\u043e\u0440\u043c\u0430\u0442 webm \u043a\u043e\u0434\u0435\u043a\u043e\u043c vp8\n              },\n              mediaRecorder = new MediaRecorder(s, recorderOptions ), \/\/ \u043e\u0431\u044a\u0435\u043a\u0442 MediaRecorder\n              socket = new WebSocket('ws:\/\/127.0.0.1:3000\/ws');\n\n               mediaRecorder.ondataavailable = function(e) {\n                if (e.data && e.data.size > 0) {\n                  \/\/ \u043f\u043e\u043b\u0443\u0447\u0430\u0435\u043c \u043a\u0443\u0441\u043e\u0447\u0435\u043a \u0432\u0438\u0434\u0435\u043e\u043f\u043e\u0442\u043e\u043a\u0430 \u0432 e.data\n                 socket.send(e.data);\n                }\n            }\n\n            mediaRecorder.start(100); \/\/ \u0434\u0435\u043b\u0438\u0442 \u043f\u043e\u0442\u043e\u043a \u043d\u0430 \u043a\u0443\u0441\u043e\u0447\u043a\u0438 \u043f\u043e 100 \u043c\u0441 \u043a\u0430\u0436\u0434\u044b\u0439\n\n        }).catch(function (err) { console.log(err); });\n}\n<\/script>\n<\/code><\/pre>\n
La parte che trasmette \u00e8 pronta! Ora proviamo a ricevere il flusso video e mostrarlo al client. Di cosa abbiamo bisogno? Prima di tutto, ovviamente, di una connessione socket. Colleghiamo un \"listener\" all'oggetto WebSocket, iscrivendoci all'evento 'message'. Una volta ricevuto un pacchetto di dati binari, il nostro server lo trasmette ai suoi iscritti, cio\u00e8 ai client. Al client si attiva una funzione di callback associata all'evento 'message', passando come argomento l'oggetto stesso \u2014 un pezzo del flusso video codificato in vp8. <\/p>\n
                        Riceviamo il flusso video<\/b><\/p>\n
<style>\n  #videoObjectHtml5ApiServer { width: 320px; height: 240px; background: #666; }\n<\/style>\n<\/head>\n<body>\n<!-- \u0417\u0434\u0435\u0441\u044c \u0432 \u044d\u0442\u043e\u043c "\u043e\u043a\u043e\u0448\u0435\u0447\u043a\u0435" \u043a\u043b\u0438\u0435\u043d\u0442 \u0431\u0443\u0434\u0435\u0442 \u0432\u0438\u0434\u0435\u0442\u044c \u0442\u0435\u0431\u044f -->\n<video autoplay id="videoObjectHtml5ApiServer"><\/video>\n\n<script type="application\/javascript">\n  var\n        video = document.getElementById('videoObjectHtml5ApiServer'),\n         socket = new WebSocket('ws:\/\/127.0.0.1:3000\/ws'), \n         arrayOfBlobs = [];\n\n         socket.addEventListener('message', function (event) {\n                \/\/ "\u043a\u043b\u0430\u0434\u0435\u043c" \u043f\u043e\u043b\u0443\u0447\u0435\u043d\u043d\u044b\u0439 \u043a\u0443\u0441\u043e\u0447\u0435\u043a \u0432 \u043c\u0430\u0441\u0441\u0438\u0432 \n                arrayOfBlobs.push(event.data);\n                \/\/ \u0437\u0434\u0435\u0441\u044c \u0431\u0443\u0434\u0435\u043c \u0447\u0438\u0442\u0430\u0442\u044c \u043a\u0443\u0441\u043e\u0447\u043a\u0438\n                readChunk();\n            });\n<\/script>\n<\/code><\/pre>\n
Per un lungo periodo ho cercato di capire perch\u00e9 non fosse possibile inviare immediatamente i pezzi ottenuti al elemento video per la riproduzione, ma si \u00e8 scoperto che assolutamente non si pu\u00f2 fare. Prima bisogna posizionare il pezzo in un buffer speciale collegato all'elemento video, e solo allora inizier\u00e0 a riprodurre il flusso video. Per fare ci\u00f2, sar\u00e0 necessario MediaSource API<\/a><\/noindex> e FileReader API<\/a><\/noindex>.<\/p>\n
MediaSource funge da intermediario tra l'oggetto di riproduzione media e la sorgente di questo flusso media. L'oggetto MediaSource contiene un buffer collegato per la sorgente del flusso video\/audio. Una caratteristica \u00e8 che il buffer pu\u00f2 contenere solo dati di tipo Uint8, quindi sar\u00e0 necessario un FileReader per creare un tale buffer. Dai un'occhiata al codice e sar\u00e0 pi\u00f9 chiaro:<\/p>\n
                        Riproduzione del flusso video<\/b><\/p>\n
<style>\n  #videoObjectHtml5ApiServer { width: 320px; height: 240px; background: #666; }\n<\/style>\n<\/head>\n<body>\n<!-- \u0417\u0434\u0435\u0441\u044c \u0432 \u044d\u0442\u043e\u043c "\u043e\u043a\u043e\u0448\u0435\u0447\u043a\u0435" \u043a\u043b\u0438\u0435\u043d\u0442 \u0431\u0443\u0434\u0435\u0442 \u0432\u0438\u0434\u0435\u0442\u044c \u0442\u0435\u0431\u044f -->\n<video autoplay id="videoObjectHtml5ApiServer"><\/video>\n\n<script type="application\/javascript">\n  var\n        video = document.getElementById('videoObjectHtml5ApiServer'),\n         socket = new WebSocket('ws:\/\/127.0.0.1:3000\/ws'),\n        mediaSource = new MediaSource(), \/\/ \u043e\u0431\u044a\u0435\u043a\u0442 MediaSource\n        vid2url = URL.createObjectURL(mediaSource), \/\/ \u0441\u043e\u0437\u0434\u0430\u0435\u043c \u043e\u0431\u044a\u0435\u043a\u0442 URL \u0434\u043b\u044f \u0441\u0432\u044f\u0437\u044b\u0432\u0430\u043d\u0438\u044f \u0432\u0438\u0434\u0435\u043e\u043f\u043e\u0442\u043e\u043a\u0430 \u0441 \u043f\u0440\u043e\u0438\u0433\u0440\u044b\u0432\u0430\u0442\u0435\u043b\u0435\u043c\n        arrayOfBlobs = [],\n        sourceBuffer = null; \/\/ \u0431\u0443\u0444\u0435\u0440, \u043f\u043e\u043a\u0430 \u043d\u0443\u043b\u044c-\u043e\u0431\u044a\u0435\u043a\u0442\n\n         socket.addEventListener('message', function (event) {\n                \/\/ "\u043a\u043b\u0430\u0434\u0435\u043c" \u043f\u043e\u043b\u0443\u0447\u0435\u043d\u043d\u044b\u0439 \u043a\u0443\u0441\u043e\u0447\u0435\u043a \u0432 \u043c\u0430\u0441\u0441\u0438\u0432 \n                arrayOfBlobs.push(event.data);\n                \/\/ \u0437\u0434\u0435\u0441\u044c \u0431\u0443\u0434\u0435\u043c \u0447\u0438\u0442\u0430\u0442\u044c \u043a\u0443\u0441\u043e\u0447\u043a\u0438\n                readChunk();\n            });\n\n         \/\/ \u043a\u0430\u043a \u0442\u043e\u043b\u044c\u043a\u043e MediaSource \u0431\u0443\u0434\u0435\u0442 \u043e\u043f\u043e\u0432\u0435\u0449\u0435\u043d , \u0447\u0442\u043e \u0438\u0441\u0442\u043e\u0447\u043d\u0438\u043a \u0433\u043e\u0442\u043e\u0432 \u043e\u0442\u0434\u0430\u0432\u0430\u0442\u044c \u043a\u0443\u0441\u043e\u0447\u043a\u0438 \n        \/\/ \u0432\u0438\u0434\u0435\u043e\/\u0430\u0443\u0434\u0438\u043e \u043f\u043e\u0442\u043e\u043a\u0430\n        \/\/ \u0441\u043e\u0437\u0434\u0430\u0435\u043c \u0431\u0443\u0444\u0435\u0440 , \u0441\u043b\u0435\u0434\u0443\u0435\u0442 \u043e\u0431\u0440\u0430\u0442\u0438\u0442\u044c \u0432\u043d\u0438\u043c\u0430\u043d\u0438\u0435, \u0447\u0442\u043e \u0431\u0443\u0444\u0435\u0440 \u0434\u043e\u043b\u0436\u0435\u043d \u0437\u043d\u0430\u0442\u044c \u0432 \u043a\u0430\u043a\u043e\u043c \u0444\u043e\u0440\u043c\u0430\u0442\u0435 \n        \/\/ \u043a\u0430\u043a\u0438\u043c \u043a\u043e\u0434\u0435\u043a\u043e\u043c \u0431\u044b\u043b \u0437\u0430\u043a\u043e\u0434\u0438\u0440\u043e\u0432\u0430\u043d \u043f\u043e\u0442\u043e\u043a, \u0447\u0442\u043e\u0431\u044b \u0442\u0435\u043c \u0436\u0435 \u0441\u043f\u043e\u0441\u043e\u0431\u043e\u043c \u043f\u0440\u043e\u0447\u0438\u0442\u0430\u0442\u044c \u0432\u0438\u0434\u0435\u043e\u043f\u043e\u0442\u043e\u043a\n         mediaSource.addEventListener('sourceopen', function() {\n            var mediaSource = this;\n            sourceBuffer = mediaSource.addSourceBuffer("video\/webm; codecs="vp8"");\n        });\n\n      function readChunk() {\n        var reader = new FileReader();\n        reader.onload = function(e) { \n          \/\/ \u043a\u0430\u043a \u0442\u043e\u043b\u044c\u043a\u043e FileReader \u0431\u0443\u0434\u0435\u0442 \u0433\u043e\u0442\u043e\u0432, \u0438 \u0437\u0430\u0433\u0440\u0443\u0437\u0438\u0442 \u0441\u0435\u0431\u0435 \u043a\u0443\u0441\u043e\u0447\u0435\u043a \u0432\u0438\u0434\u0435\u043e\u043f\u043e\u0442\u043e\u043a\u0430\n          \/\/ \u043c\u044b "\u043f\u0440\u0438\u0446\u0435\u043f\u043b\u044f\u0435\u043c" \u043f\u0435\u0440\u0435\u043a\u043e\u0434\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u044b\u0439 \u0432 Uint8Array (\u0431\u044b\u043b Blob) \u043a\u0443\u0441\u043e\u0447\u0435\u043a \u0432 \u0431\u0443\u0444\u0435\u0440, \u0441\u0432\u044f\u0437\u0430\u043d\u043d\u044b\u0439\n          \/\/ \u0441 \u043f\u0440\u043e\u0438\u0433\u0440\u044b\u0432\u0430\u0442\u0435\u043b\u0435\u043c, \u0438 \u043f\u0440\u043e\u0438\u0433\u0440\u044b\u0432\u0430\u0442\u0435\u043b\u044c \u043d\u0430\u0447\u0438\u043d\u0430\u0435\u0442 \u0432\u043e\u0441\u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0438\u0442\u044c \u043f\u043e\u043b\u0443\u0447\u0435\u043d\u043d\u044b\u0439 \u043a\u0443\u0441\u043e\u0447\u0435\u043a \u0432\u0438\u0434\u0435\u043e\/\u0430\u0443\u0434\u0438\u043e\n          sourceBuffer.appendBuffer(new Uint8Array(e.target.result));\n\n          reader.onload = null;\n        }\n        reader.readAsArrayBuffer(arrayOfBlobs.shift());\n      }\n<\/script>\n<\/code><\/pre>\n
Il prototipo del servizio di streaming \u00e8 pronto. Il principale svantaggio \u00e8 che la riproduzione video sar\u00e0 in ritardo rispetto alla parte trasmittente di 100 ms, impostato da noi stessi durante la suddivisione del flusso video prima della trasmissione al server. Inoltre, quando controllavo sul mio laptop, accumulavo gradualmente un lag tra il lato trasmittente e quello ricevente, il che era chiaramente visibile. Ho iniziato a cercare modi per affrontare questo problema e\u2026 sono capitato su RTCPeerConnection API<\/a><\/noindex>, che consente di trasmettere il flusso video senza trucchi come la suddivisione del flusso in pezzi. Il lag accumulato, penso, deriva dal fatto che nel browser avviene la ricodifica di ogni pezzo in formato webm prima della trasmissione. Non ho voluto indagare oltre e ho iniziato ad approfondire WebRTC; credo che scriver\u00f2 un articolo separato sui risultati delle mie ricerche, se lo considerer\u00f2 interessante per la comunit\u00e0.
\n
Fonte: habr.com<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"
\u0412 \u0441\u0442\u0430\u0442\u044c\u0435 \u044f \u0445\u043e\u0447\u0443 \u043f\u043e\u0434\u0435\u043b\u0438\u0442\u044c\u0441\u044f \u0441\u0432\u043e\u0438\u043c\u0438 \u043f\u043e\u043f\u044b\u0442\u043a\u0430\u043c\u0438 \u0441\u0434\u0435\u043b\u0430\u0442\u044c \u0441\u0442\u0440\u0438\u043c\u043c\u0438\u043d\u0433 \u0432\u0438\u0434\u0435\u043e \u0447\u0435\u0440\u0435\u0437 websockets \u0431\u0435\u0437 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u044f \u0441\u0442\u043e\u0440\u043e\u043d\u043d\u0438\u0445 \u043f\u043b\u0430\u0433\u0438\u043d\u043e\u0432 \u0431\u0440\u0430\u0443\u0437\u0435\u0440\u0430 \u0442\u0438\u043f\u0430 Adobe Flash Player. \u0427\u0442\u043e \u0438\u0437 \u044d\u0442\u043e\u0433\u043e \u043f\u043e\u043b\u0443\u0447\u0438\u043b\u043e\u0441\u044c \u0447\u0438\u0442\u0430\u0439\u0442\u0435 \u0434\u0430\u043b\u0435\u0435. Adobe Flash \u2014 \u0440\u0430\u043d\u0435\u0435 Macromedia Flash, \u044d\u0442\u043e \u043f\u043b\u0430\u0442\u0444\u043e\u0440\u043c\u0430 \u0434\u043b\u044f \u0441\u043e\u0437\u0434\u0430\u043d\u0438\u044f \u043f\u0440\u0438\u043b\u043e\u0436\u0435\u043d\u0438\u0439, \u0440\u0430\u0431\u043e\u0442\u0430\u044e\u0449\u0438\u0445 \u0432 \u0432\u0435\u0431-\u0431\u0440\u0430\u0443\u0437\u0435\u0440\u0435. \u0414\u043e \u0432\u043d\u0435\u0434\u0440\u0435\u043d\u0438\u044f Media Stream API \u044d\u0442\u043e \u0431\u044b\u043b\u0430 \u043f\u0440\u0430\u043a\u0442\u0438\u0447\u0435\u0441\u043a\u0438 \u0435\u0434\u0438\u043d\u0441\u0442\u0432\u0435\u043d\u043d\u0430\u044f \u043f\u043b\u0430\u0442\u0444\u043e\u0440\u043c\u0430 \u0434\u043b\u044f \u0441\u0442\u0440\u0438\u043c\u043c\u0438\u043d\u0433\u0430 \u0441 \u0432\u0435\u0431-\u043a\u0430\u043c\u0435\u0440\u044b […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[688],"tags":[],"class_list":["post-94138","post","type-post","status-publish","format-standard","hentry","category-administrirovanie"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47(Quasi) streaming inutile della webcam dal browser. Media Stream e Websockets | ProHoster","description":"Nell'articolo voglio condividere i miei tentativi di fare streaming video tramite websockets senza utilizzare plugin esterni come Adobe Flash Player.","canonical_url":"https:\/\/prohoster.info\/it\/blog\/administrirovanie\/pochti-bespoleznyj-striming-vebkamery-iz-brauzera-media-stream-i-websockets","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"it_IT","og:site_name":"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b","og:type":"article","og:title":"\ud83e\udd47(\u041f\u043e\u0447\u0442\u0438) \u0431\u0435\u0441\u043f\u043e\u043b\u0435\u0437\u043d\u044b\u0439 \u0441\u0442\u0440\u0438\u043c\u0438\u043d\u0433 \u0432\u0435\u0431\u043a\u0430\u043c\u0435\u0440\u044b \u0438\u0437 \u0431\u0440\u0430\u0443\u0437\u0435\u0440\u0430. Media Stream \u0438 Websockets | ProHoster","og:description":"\u0412 \u0441\u0442\u0430\u0442\u044c\u0435 \u044f \u0445\u043e\u0447\u0443 \u043f\u043e\u0434\u0435\u043b\u0438\u0442\u044c\u0441\u044f \u0441\u0432\u043e\u0438\u043c\u0438 \u043f\u043e\u043f\u044b\u0442\u043a\u0430\u043c\u0438 \u0441\u0434\u0435\u043b\u0430\u0442\u044c \u0441\u0442\u0440\u0438\u043c\u043c\u0438\u043d\u0433 \u0432\u0438\u0434\u0435\u043e \u0447\u0435\u0440\u0435\u0437 websockets \u0431\u0435\u0437 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u044f \u0441\u0442\u043e\u0440\u043e\u043d\u043d\u0438\u0445 \u043f\u043b\u0430\u0433\u0438\u043d\u043e\u0432 \u0431\u0440\u0430\u0443\u0437\u0435\u0440\u0430 \u0442\u0438\u043f\u0430 Adobe Flash Player.","og:url":"https:\/\/prohoster.info\/it\/blog\/administrirovanie\/pochti-bespoleznyj-striming-vebkamery-iz-brauzera-media-stream-i-websockets","og:image":"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg","og:image:secure_url":"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg","og:image:width":350,"og:image:height":350,"article:published_time":"2020-09-13T05:42:42+00:00","article:modified_time":"2020-09-13T05:42:42+00:00","article:publisher":"https:\/\/www.facebook.com\/prohoster","article:author":"https:\/\/www.facebook.com\/prohoster"},"aioseo_meta_data":{"post_id":"94138","title":null,"description":null,"keywords":null,"keyphrases":null,"primary_term":null,"canonical_url":null,"og_title":null,"og_description":null,"og_object_type":"default","og_image_type":"default","og_image_url":null,"og_image_width":null,"og_image_height":null,"og_image_custom_url":null,"og_image_custom_fields":null,"og_video":null,"og_custom_url":null,"og_article_section":null,"og_article_tags":null,"twitter_use_og":false,"twitter_card":"default","twitter_image_type":"default","twitter_image_url":null,"twitter_image_custom_url":null,"twitter_image_custom_fields":null,"twitter_title":null,"twitter_description":null,"schema":{"blockGraphs":[],"customGraphs":[],"default":{"data":{"Article":[],"Course":[],"Dataset":[],"FAQPage":[],"Movie":[],"Person":[],"Product":[],"ProductReview":[],"Car":[],"Recipe":[],"Service":[],"SoftwareApplication":[],"WebPage":[]},"graphName":"","isEnabled":true},"graphs":[]},"schema_type":null,"schema_type_options":null,"pillar_content":false,"robots_default":true,"robots_noindex":false,"robots_noarchive":false,"robots_nosnippet":false,"robots_nofollow":false,"robots_noimageindex":false,"robots_noodp":false,"robots_notranslate":false,"robots_max_snippet":null,"robots_max_videopreview":null,"robots_max_imagepreview":"large","priority":null,"frequency":null,"local_seo":null,"seo_analyzer_scan_date":null,"breadcrumb_settings":null,"limit_modified_date":false,"reviewed_by":null,"ai":null,"created":"2021-02-28 11:32:23","updated":"2022-10-01 11:18:30","focus_keyword":null,"additional_keywords":null,"truseo_locale":null},"gt_translate_keys":[{"key":"link","format":"url"}],"_links":{"self":[{"href":"https:\/\/prohoster.info\/it\/wp-json\/wp\/v2\/posts\/94138","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/prohoster.info\/it\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/prohoster.info\/it\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/prohoster.info\/it\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/prohoster.info\/it\/wp-json\/wp\/v2\/comments?post=94138"}],"version-history":[{"count":0,"href":"https:\/\/prohoster.info\/it\/wp-json\/wp\/v2\/posts\/94138\/revisions"}],"wp:attachment":[{"href":"https:\/\/prohoster.info\/it\/wp-json\/wp\/v2\/media?parent=94138"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/prohoster.info\/it\/wp-json\/wp\/v2\/categories?post=94138"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/prohoster.info\/it\/wp-json\/wp\/v2\/tags?post=94138"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}