Bitrate Selection

Methods and options removed

The v4.0.0 release totally changes how Representations (a.k.a. qualities or profiles) selection works. Previously, this selection was only based on bitrate settings. It is now more explicit by directly allowing an application to select which Representation(s) it wants to be able to play.

Due to this, v3.x.x methods related to controlling the current audio and video bitrate:

  • setMinVideoBitrate
  • setMinAudioBitrate
  • getMinVideoBitrate
  • getMinAudioBitrate
  • setMaxVideoBitrate
  • setMaxAudioBitrate
  • getMaxVideoBitrate
  • getMaxAudioBitrate
  • setVideoBitrate
  • setAudioBitrate
  • getManualVideoBitrate
  • getManualAudioBitrate

As well as the following constructor options:

  • minVideoBitrate
  • minAudioBitrate
  • maxVideoBitrate
  • maxAudioBitrate

Have all been removed.

Why was those removed?

When drafting a better API for Representation selection than what we had before, we finally reached a point where we were constructing an API that would allow to replicate all those methods and options. Even better, they could now be based on any criteria (e.g. on the video quality's height, framerate, codecs, decipherability status etc.), and not just its bitrate.

This, and the fact that the specific audio or video quality's bitrate might not always be known depending on the streaming technology, led us to remove the previous bitrate-specific API to the more general and powerful "Representations locking" API that will be shown in this page.

How to replace them

Semantic of the previous API

What the bitrate methods and options were doing was basically to restrain the pool of Representation the RxPlayer would chose from based on each of those object's bitrate property.

Basically, calling setMaxVideoBitrate(1000) / maxVideoBitrate: 1000 would filter out all video Representation whose bitrate was higher than 1000 (with an exception if no Representation passed that test, in which case it would take the Representation(s) with the lowest bitrate instead).

Likewise setMinVideoBitrate(1000) / minVideoBitrate: 1000 would the other way around filter out all video Representation was lower than 1000 (with again the same exception than the maxVideoBitrate one, only the highest bitrate now).

At last setVideoBitrate(1000) would select the Representation with a bitrate set exactly to 1000, immediately lower if not found, or the closest if no Representation has a bitrate lower or equal to 1000.

Now: Locking Representations explicitly

Now, there's a new set of methods and options allowing to explicitly filter Representation based on any criteria you want and for any choosen track:

  • the lockVideoRepresentations and lockAudioRepresentations methods, only authorize respectively some video and some audio Representation from being played by the RxPlayer.

    For example to only allows some video Representations called "repA" and "repB", for the current Period (that is: the content being played right now), you could write:

    rxPlayer.lockVideoRepresentations([repA.id, repB.id]);

  • setAudioTrack and setVideoTrack now also allows to only authorize some audio and video Representation from being played in the chosen track by setting a lockedRepresentations property.

    For example to only allow the Representations "rep1" and "rep2" in a new audio track "aTrack", you could write:

    rxPlayer.setAudioTrack({
  trackId: aTrack.id,
  lockedRepresentations: [rep1.id, rep2.id],
});

  • the getLockedVideoRepresentations and getLockedAudioRepresentations), methods allows to get the list of respectively the currently locked video and audio Representations, or null if none are locked for that type:

    const lockedVideoRepresentations = rxPlayer.getLockedVideoRepresentations();
if (lockedVideoRepresentations === null) {
  console.log("There's no video Representation locked for the current content");
} else {
  console.log(
    "`id` property of the video Representations locked for the current content:",
    lockedVideoRepresentations
  );
}

  • the unlockVideoRepresentations and unlockAudioRepresentations methods, allows to unlock previously respectively "locked" video and audio Representations.

    // Re-enable all video Representations (which previously have been
// restrained for example by a `lockVideoRepresentations` call:
rxPlayer.unlockVideoRepresentations();

Obtaining the Representation objects

As for the Representation objects themselves, they can for example be obtained by using:

  • getVideoTrack for a currently-chosen video track, through its representations property, whose content is an array of elements each describing a Representation linked to that video track.

    const currentVideoTrack = rxPlayer.getVideoTrack();
console.log(
  "This video track has " +
  currentVideoTrack.representations.length +
  " different video Representation(s)"
);
for (let i = 0; i < currentVideoTrack.representations.length; i++) {
  console.log(
    "The Representation number " + i + " has a bitrate set to: " +
    currentVideoTrack.representations[i].bitrate
  );
}

  • getAudioTrack for a currently-chosen audio track, again through its representations property.

    const currentAudioTrack = rxPlayer.getAudioTrack();
console.log(
  "This audio track has " +
  currentAudioTrack.representations.length +
  " different audio Representation(s)"
);

  • getAvailableVideoTracks for all available video tracks linked to a Period, here the representations property is still present on each "track object" returned by that method.

    const trackList = rxPlayer.getAvailableVideoTracks();
console.log(`There are currently ${trackList.length} video track(s) available`);
for (let i = 0; i < trackList.representations.length; i++) {
  console.log("Data for video track number " + i + ":");
  const videoTrack = trackList[i];
  for (let j = 0; j < videoTrack.representations.length; j++) {
    console.log(
      "Its Representation number " + j + " has an height set to: " +
      videoTrack.representations[j].height
    );
  }
}

  • getAvailableAudioTracks for all available audio tracks linked to a Period, also through a representations property.

    const trackList = rxPlayer.getAvailableAudioTracks();
console.log(`There are currently ${trackList.length} audio track(s) available`);

  • The videoTrackChange, audioTrackChange, availableVideoTracksChange and availableAudioTracksChange player events which respectively emit data similar to the getVideoTrack, getAudioTrack, getAvailableVideoTracks and getAvailableAudioTracks methods.

Global idea to replace the previous API

Thus the idea would be now to, for each set video track, to explicitly select the Representation(s) you want, based on the criteria you want.

For example, to only play the video Representation(s) which have a bitrate set to 500 for the current content, you could write:

const currentVideoTrack = rxPlayer.getVideoTrack();
const representations500 = currentVideoTrack.representations.filter(r => {
  return r.bitrate === 500;
});
if (representations500.length > 0) {
  // Note: It's only the `id` property that is wanted here
  const representationsId = representations500.map(r => r.id);
  rxPlayer.lockVideoRepresentations(representationsId);
}

Reacting to the lock "breaking"

In rare and very specific situations, locked Representation may all become unplayable during playback. This can for example happen when all the locked Representations appear to be undecipherable once their licence have been fetched.

Instead of stopping on error when this happens, the RxPlayer choose to "break the lock", which means it goes back to play all Representation from the chosen track. Just before doing that, it emits the "brokenRepresentationsLock" event, allowing you to react to this.

In the context of replacing bitrate API, you may want to profit from this event to re-apply the bitrate limitation you had - or to stop the content if you want to.

For example, only play the lowest video bitrate after the lock is broken, you can write:

player.addEventListener("brokenRepresentationsLock", (data) => {
  const videoTrack = rxPlayer.getVideoTrack(data.period.id);
  const lowestBitrate = videoTrack.representations.reduce((acc, r) => {
    if (acc === undefined || acc.bitrate === undefined) {
      return r;
    }
    if (r.bitrate !== undefined && r.bitrate < acc.bitrate) {
      return r;
    }
    return acc;
  }, undefined);
  if (lowestBitrate !== undefined) {
    rxPlayer.lockVideoRepresentations({
      representations: [lowestBitrate.id],
      periodId: data.period.id,
    });
  }
}

Switching at new "Periods"

The "Period" notion allows for example to handle several Representation choices on DASH contents with multiple <Period> elements, each with its own list of tracks and thus, Representation linked to it.

For example you could consider an old film only available with video Representations up to 720p followed by a football match with video Representations ranging up to UHD. Here we would have two periods, each with its own tracks and Representations.

To know the list of periods currently considered by the RxPlayer, you can now call the getAvailablePeriods RxPlayer method:

const periods = rxPlayer.getAvailablePeriods();

To be notified when new Periods are being considered by the RxPlayer, you can react to the new newAvailablePeriods RxPlayer event:

rxPlayer.addEventListener("newAvailablePeriods", (periods) => {
  // Do things with those periods
});

Most methods exposed in this page, whether they are for Representations locking or the tracks API, allow to precize which Period you're talking about (if it's not communicated, the RxPlayer will assume that you're talking about the currently-playing one).

For example, to only lock the first video Representation of the first considered Period you can do:

const periods = rxPlayer.getAvailablePeriods();
if (periods.length > 0) {
  const firstPeriodVideoTrack = rxPlayer.getVideoTrack(periods[0].id);
  if (firstPeriodVideoTrack.representations.length > 0) {
    rxPlayer.lockVideoRepresentations({
      representations: [firstPeriodVideoTrack.representations[0].id],
      periodId: periods[0].id,
    });
  }
}

Locking each time a track is chosen

The choice of Representation has to be performed basically at each new chosen track, whether it is for a new Period or an already-known one whose track has been changed.

The former (new periods) can be reacted to via the "newAvailablePeriods" events we wrote about in previous chapters.

The latter (track change, for any Period) now also has its own event "trackUpdate".

For example to only play the video Representations whose bitrate is inferior or equal to 1000000, you can write:

player.addEventListener("trackUpdate", (data) => {
  const videoTrack = rxPlayer.getVideoTrack(data.period.id);
  const filtered = videoTrack.representations.filter((r) => {
    return r.bitrate !== undefined && r.bitrate <= 1000000;
  });
  if (filtered.length > 0) {
    rxPlayer.lockVideoRepresentations({
      representations: filtered,
      periodId: data.period.id,
    });
  } else {
    // To be defined on your side what you want to do here
  }
}

Full examples of bitrate selection replacements

setMaxVideoBitrate / maxVideoBitrate / setMaxAudioBitrate / maxAudioBitrate

The following examples only talk about the video variants of these API to simplify, but it can be applied to the audio variant.

To replace the setMaxVideoBitrate method or the maxVideoBitrate option, we will first declare a function replicating its behavior for a given bitrate and Period:

function lockMaxBitrateForPeriod(maxBitrate, period) {
  if (maxBitrate === Infinity) {
    // /!\ If you also have other bitrate restrictions, you may not want to
    // unlock here
    rxPlayer.unlockVideoRepresentations(period.id);
  } else {
    const videoTrack = rxPlayer.getVideoTrack(period.id);
    const representationIds = videoTrack.representations.reduce(
      (acc, representation) => {
        if (
          representation.bitrate !== undefined &&
          representation.bitrate <= maxBitrate
        ) {
          acc.push(representation.id);
        }
        return acc;
      },
      [],
    );

    if (representationIds.length > 0) {
      rxPlayer.lockVideoRepresentations({
        periodId: period.id,
        representations: representationIds,
      });
    } else {
      // Special case for when no Representation respects the maximum bitrate:
      // Lock Representation(s) with the lowest bitrate
      const lowestBitrate = videoTrack.representations
        .map((representation) => representation.bitrate)
        .filter((representation) => representation !== undefined)
        .sort((a, b) => a - b)[0];
      if (lowestBitrate === undefined) {
        rxPlayer.unlockVideoRepresentations(period.id);
      } else {
        rxPlayer.lockVideoRepresentations({
          periodId: period.id,
          representations: videoTrack.representations.filter(
            (representation) => representation.bitrate <= lowestBitrate,
          ),
        });
      }
    }
  }
}

Then we want to apply it each times a new Period is available and each time the track for any Period is changed:

rxPlayer.addEventListener("newAvailablePeriods", (periods) => {
  for (let i = 0; i < periods.length; i += 1) {
    lockMaxBitrateForPeriod(
      maxBitrate, // To set to the bitrate wanted
      periods[i],
    );
  }
});

rxPlayer.addEventListener("trackUpdate", (data) => {
  lockMaxBitrateForPeriod(
    maxBitrate, // To set to the bitrate wanted
    data.period,
  );
});

Because we might want to still re-apply the same logic when/if the lock is broken, we can also add:

rxPlayer.addEventListener("brokenRepresentationsLock", (data) => {
  lockMaxBitrateForPeriod(
    maxBitrate, // To set to the bitrate wanted
    data.period,
  );
});

And finally, if you want to apply the maximum bitrate while the content is already playing, you can write:

const periods = rxPlayer.getAvailablePeriods();
for (let i = 0; i < periods.length; i += 1) {
  const period = periods[i];
  lockMaxBitrateForPeriod(
    maxBitrate, // To set to the bitrate wanted
    period,
  );
}

setMinVideoBitrate / minVideoBitrate / setMinAudioBitrate / minAudioBitrate

The following examples only talk about the video variants of these API to simplify, but it can be applied to the audio variant.

Replacing the setMinVideoBitrate method or the minVideoBitrate option is very close than what has to be done to replace the setMaxVideoBitrate method and / or the maxVideoBitrate option. Because of these we will only here describe a lockMinBitrateForPeriod function, which is supposed to be the lockMaxBitrateForPeriod function equivalent for minimum bitrates:

function lockMinBitrateForPeriod(minBitrate, period) {
  if (minBitrate === 0) {
    // /!\ If you also have other bitrate restrictions, you may not want to
    // unlock here
    rxPlayer.unlockVideoRepresentations(period.id);
  } else {
    const videoTrack = rxPlayer.getVideoTrack(period.id);
    const representationIds = videoTrack.representations.reduce(
      (acc, representation) => {
        if (
          representation.bitrate !== undefined &&
          representation.bitrate >= minBitrate
        ) {
          acc.push(representation.id);
        }
        return acc;
      },
      [],
    );

    if (representationIds.length > 0) {
      rxPlayer.lockVideoRepresentations({
        periodId: period.id,
        representations: representationIds,
      });
    } else {
      // Special case for when no Representation respects the minimum bitrate:
      // Lock Representation(s) with the highest bitrate
      const highestBitrate = videoTrack.representations
        .map((representation) => representation.bitrate)
        .filter((representation) => representation !== undefined)
        .sort((a, b) => b - a)[0];
      if (highestBitrate === undefined) {
        rxPlayer.unlockVideoRepresentations(period.id);
      } else {
        rxPlayer.lockVideoRepresentations({
          periodId: period.id,
          representations: videoTrack.representations.filter(
            (representation) => representation.bitrate >= highestBitrate,
          ),
        });
      }
    }
  }
}

setAudioBitrate / setVideoBitrate

The following examples only talk about the video variants of these API to simplify, but it can be applied to the audio variant.

Replacing the setVideoBitrate method is very close than what has to be done to replace the setMaxVideoBitrate method or the maxVideoBitrate option. Because of these we will only here describe a lockBitrateForPeriod function, which is supposed to be the lockMaxBitrateForPeriod function equivalent for a chosen bitrates:

function lockBitrateForPeriod(bitrate, period) {
  if (bitrate === 0) {
    // /!\ If you also have other bitrate restrictions, you may not want to
    // unlock here
    rxPlayer.unlockVideoRepresentations(period.id);
  } else {
    const videoTrack = rxPlayer.getVideoTrack(period.id);
    const filteredReps = videoTrack.representations
      .filter((representation) => {
        return (
          representation.bitrate !== undefined &&
          representation.bitrate <= bitrate
        );
      });

    if (filteredReps.length > 0) {
      const highestBitrateId = filteredReps
        .sort((a, b) => b.bitrate - a.bitrate)[0];
      rxPlayer.lockVideoRepresentations({
        periodId: period.id,
        representations: [highestBitrateId],
      });
    } else {
      // Special case for when no Representation respects the given bitrate:
      // Lock Representation(s) with the lowest bitrate
      const lowestBitrate = videoTrack.representations
        .map((representation) => representation.bitrate)
        .filter((representation) => representation !== undefined)
        .sort((a, b) => a - b)[0];
      if (lowestBitrate === undefined) {
        rxPlayer.unlockVideoRepresentations(period.id);
      } else {
        rxPlayer.lockVideoRepresentations({
          periodId: period.id,
          representations: videoTrack.representations.filter(
            (representation) => representation.bitrate <= lowestBitrate,
          ),
        });
      }
    }
  }
}

Bitrate Selection

Page List