--- title: "Make a video play in browsers in C# (MakePlayable)" url: https://recursiveai.org/onemedia/cookbook/make-video-playable-in-browser/ description: "Make a video play in browsers in C#: OneMedia’s MakePlayable moves the MP4 index to the front, remuxes MKV into MP4 or WebM, and re-encodes audio such as Vorbis to Opus for a browser profile, without re-encoding video. Output checked with ffprobe and headless Chrome." version: "0.3.0-preview.2" --- # Make a video play in browsers in C# (MakePlayable) `AudioTranscoder.MakePlayable(input, output, profile)` turns a file a browser profile can’t play into one it can. It does the least that works: moves an MP4’s index to the front, remuxes into a container the browser takes, or re-encodes an audio track to Opus when that’s the only other thing in the way. Video is never re-encoded; a video codec the browser lacks is reported, not fixed. The inputs are the Sintel trailer (CC BY 3.0, © copyright Blender Foundation | durian.blender.org), whose index is at the end, a copy of it made with FFmpeg as MKV with Vorbis audio (the video copied, the audio encoded), and MDN’s CC0 flower clip as WebM (VP8/Vorbis). ```shell dotnet new console -o MakePlayable && cd MakePlayable dotnet add package RecursiveAI.OneMedia.Audio --version 0.3.0-preview.2 curl -L -o sintel.mp4 https://download.blender.org/durian/trailer/sintel_trailer-480p.mp4 curl -L -o flower.webm https://interactive-examples.mdn.mozilla.net/media/cc0-videos/flower.webm ffmpeg -v error -i sintel.mp4 -c:v copy -c:a libvorbis -q:a 4 sintel-vorbis.mkv ``` `RecursiveAI.OneMedia.Audio` brings in the core package and [OneAudio](https://recursiveai.org/oneaudio/), which does the audio decoding and the Opus encoding. Put this in `Program.cs` and run `dotnet run`: ```csharp using RecursiveAI.OneMedia.Audio; using RecursiveAI.OneMedia.Playback; Make("sintel-vorbis.mkv", "sintel-safari.mp4", BrowserProfiles.Safari); Make("sintel.mp4", "sintel-chrome.mp4", BrowserProfiles.Chrome); Make("sintel-vorbis.mkv", "sintel-generic.mp4", BrowserProfiles.GenericMp4); Make("flower.webm", "flower-ios.mp4", BrowserProfiles.IosSafari); static void Make(string input, string output, BrowserProfile profile) { MakePlayableReport report = AudioTranscoder.MakePlayable(input, output, profile); Console.WriteLine($"{input} for {profile.Id}: {report.Status}" + (report.Target is { } target ? $", written as {target}" : "")); foreach (MakePlayableAction action in report.Actions) Console.WriteLine($" {action.Kind}: {action.Detail}"); foreach (PlaybackBlocker blocker in report.Remaining) Console.WriteLine($" still blocked: {blocker.Code}: {blocker.Message}"); } ``` ```text sintel-vorbis.mkv for safari: Made, written as Mp4 Remux: Copy the tracks into mp4, movie box first. TranscodeAudio: Audio track 1: vorbis to opus, 96000 bit/s, 48000 Hz, 2 ch, encoder delay 312/48000 s. sintel.mp4 for chrome: Made Faststart: Moved the 39456-byte movie box in front of the media data. sintel-vorbis.mkv for generic-mp4: Refused still blocked: transcode.no-target: Generic MP4 plays none of the codecs an audio transcode can produce (opus) in mp4. flower.webm for ios-safari: Refused still blocked: codec.unsupported: Safari (iOS) does not play vp8. ``` - **MKV with Vorbis, for Safari.** Safari doesn’t take Matroska, and in the containers it does take it doesn’t play Vorbis, so the H.264 is remuxed into MP4 and the Vorbis is re-encoded to Opus at 96 kbit/s; the video packets are copied. - **MP4 with its index at the end, for Chrome.** Chrome plays it already, but only after fetching the end of the file, so the movie box is moved to the front ([MP4 faststart](https://recursiveai.org/onemedia/cookbook/mp4-faststart/)); everything else is copied by range. - **The same MKV, for the generic MP4 profile.** That profile plays AAC and MP3 but not Opus, and Opus is the only audio MakePlayable can produce, so it refuses with `transcode.no-target` and writes nothing. - **VP8 for iOS Safari.** A video blocker: nothing is written, and the report says why. `report.Status` is `AlreadyPlayable` (copied as it is), `Made`, `NeedsAudioTranscode` (only from the core’s `Media.MakePlayable`, which has no transcoder), `Refused` or `Failed`. The report also holds the verdicts before and after (`Before`, `After`), the remux report (`Remux`) and each audio transcode (`AudioTranscodes`). The output is judged by opening it and asking `CanPlay` again; one that still doesn’t play is deleted and reported as `Failed`. So is a remux that would leave out the video, or all of the audio: the status is `Failed`, nothing is written, and `report.Remaining` holds a `remux.dropped-track` blocker for each lost track. A `Made` file has the picture and sound the input had. ## The audio target is Opus only From the project’s [MakePlayable page](https://recursiveai.org/onemedia/docs/make-playable/): “Opus is the one target; profiles that play neither Opus nor what the file has (`generic-mp4`) refuse.” The encode is “Opus, 48 kHz, mono or stereo, 20 ms packets, OneAudio’s Opus encoder”, at 64 kbit/s mono or 96 kbit/s stereo by default (`MakePlayableOptions.AudioBitRate`), and the input is decoded by OneAudio first: AAC-LC, MP3, Vorbis, FLAC, Opus and AMR, or PCM. AC-3, E-AC-3, ALAC and WMA have no decoder and are refused with `transcode.no-decoder`; more than two channels with `transcode.channels`. ## Check it with ffprobe ```shell ffprobe -v error -show_entries stream=index,codec_name,sample_rate,channels:format=format_name,duration -of compact sintel-safari.mp4 ``` ```text stream|index=0|codec_name=h264 stream|index=1|codec_name=opus|sample_rate=48000|channels=2 format|format_name=mov,mp4,m4a,3gp,3g2,mj2|duration=52.208000 ``` The video comes through whole: ffprobe decodes 1,253 frames from both the source and the written MP4. ```shell for f in sintel.mp4 sintel-safari.mp4; do ffprobe -v error -count_frames -select_streams v:0 -show_entries stream=nb_read_frames -of csv=p=0 $f; done ``` ```text 1253 1253 ``` ## Checked in headless Chrome The two written files were served over HTTP with range requests, loaded into a `