HTTP Live Streaming (HLS) authoring specification for Apple devices

Overview

For a deeper discussion of the features available in HLS, refer to Apple’s streaming resource page, which contains pointers to the overview document, the HLS specification, technical notes, tools, presentations, and examples.

About HLS authoring

The HLS specification is a published RFC (RFC 8216). However, HLS continues to evolve, so there’s an updated draft specification — draft-pantos-hls-rfc8216bis (HLS2).

Please see Documentation, which may contain a reference to a preliminary version of the draft specification.

This document always uses the most up-to-date version, which is, either the preliminary version or the draft specification (whichever has a higher version number).

The key words “MUST,” “MUST NOT,” “REQUIRED,” “SHALL,” “SHALL NOT,” “SHOULD,” “SHOULD NOT,” “RECOMMENDED,” “MAY,” and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.

Find additional information for HLS specifications at HTTP Live Streaming (HLS) Authoring Specification for Apple devices appendixes.

About spatial video

Spatial video is intended to produce a richer experience for the user. Spatial video MUST use the REQ-VIDEO-LAYOUT attribute to specify desired channel and projection specifiers. Please see HLS specification for valid channel and projection specifiers.

Spatial video media is split into following categories.

Stereo Video

Similar to Stereo audio, which indicates different audio for the left and the right ear, visual media can be stereoscopic in which a separate view is available for the left eye and another view is available to be presented simultaneously to the right eye.

Projection Video

Rectilinear projection is default for the video media which indicates there is no further processing necessary to present the video. Content creators can opt for non rectilinear projections to preserve the artistic intent. Please refer to HLS specification for possible non-rectilinear projections. This content is categorized under Apple Projected Media Profile (APMP) and can be monoscopic or stereo.

Immersive Video

This video is projected from a hemisphere (typically a special lens) and often requires a special metadata file in order render correctly.

This video relies on a special projection type, known as ‘PROJ-AIV’ which is defined outside the core HLS specification. For details, see QuickTime and ISO Base Media File Formats and Spatial and Immersive Media

About multi-format audio codecs

Multi-format audio codecs support combinations of channels, audio objects, and ambisonics as opposed to multi-channel codecs that just support channels. Examples of such a multi-format codec are:

• Apple Positional Audio Codec APAC

• Dolby Digital Plus JOC

General authoring requirements

A stream that matches these requirements should be compatible with iOS, tvOS, macOS or visionOS. Rules with a leading asterisk (*) are modified by one or more of the Amended Requirements listed below.

Support for a specific video Profile and Level doesn’t imply that any particular device supports the maximum bit rate for that Level.

Video

1. Video encoding requirements

1.1. All video MUST be encoded using H.264/AVC, HEVC/H.265, Dolby Vision, or AV1.

1.2. The container format for H.264 video MUST be fragmented MP4 (fMP4) files or MPEG transport streams.

1.3.

1.3a. * For maximum compatibility, some H.264 variants SHOULD be less than or equal to High Profile, Level 4.1.

1.3b. * Profile and Level for H.264 MUST be less than or equal to High Profile, Level 5.2.

1.4. For H.264, you SHOULD use High Profile in preference to Main or Baseline Profile.

1.5. The container format for HEVC video MUST be fMP4.

1.6.

1.6a. * For maximum compatibility, some HEVC variants SHOULD be less than or equal to Main 10 Profile, Level 4.0, Main Tier.

1.6b. * Profile, Level, and Tier for HEVC MUST be less than or equal to Main 10 Profile, Level 5.1, High Tier.

1.7. High Dynamic Range (HDR) HEVC video MUST be HDR10, HLG, or Dolby Vision.

1.8. For HDR10 video, the SEI NAL units (that is, static metadata) SHOULD be in the HEVC Configuration Box ('hvcC') and not in the individual sample data.

1.9. * Profile and Level for Dolby Vision MUST be Profile 5 (single layer 10-bit HEVC) and less than or equal to Level 7.

1.10. You SHOULD use video formats in which the parameter sets are stored in the sample descriptions, rather than the samples. (That is, use 'avc1', 'hvc1', or 'dvh1' rather than 'avc3', 'hev1', or 'dvhe'.)

1.11. For backward compatibility, content SHOULD NOT use a higher level than required by the content resolution and frame rate.

1.12. * For backward compatibility, some video content SHOULD be encoded with H.264.

1.13. Key frames (IDRs) SHOULD be present every two seconds.

1.14. All interlaced source content MUST be deinterlaced.

1.15. You SHOULD deinterlace 30i content to 60p instead of 30p.

1.16. Live (linear) video from NTSC or ATSC source SHOULD be 60 or 59.94 fps.

1.17. Live (linear) video from PAL source SHOULD be 50 fps.

1.18. Video on Demand (VOD) content SHOULD use a natural frame rate for the content. Frame rates 23.976, 24, 25, 29.97, 30, 50, 59.94, and 60 fps are supported.

1.19. Frame rates above 60 fps SHALL NOT be used.

1.20. * For HDR content, frame rates less than or equal to 30 fps SHOULD be provided.

1.21. Streams SHOULD use a single color space — one of either Rec. 601, Rec. 709, DCI-P3, or Rec. 2020.

1.22. For VOD, the color space SHOULD be the original color space of the material.

1.23. * If multiple video streams are provided (H.264, HEVC, HDR), each stream SHOULD provide all anticipated bandwidths. Clients SHOULD NOT be required to switch codecs.

1.24. * For backward compatibility, SDR streams MUST be provided. (See also item 6.16.)

1.25. * There are many possible choices of bit rates for variants. The following tables provide one possible set of bit rate variants. (See On bit rates for variants for additional considerations.)

Following tables provide a possible bit rate recommendations for APMP videos.

APMP monoscopic videos:

If the quality of the 3rd tier is not acceptable, or you are working with very high motion content, one can lower the resolution and bitrate combination further.

APMP stereoscopic videos:

If the quality of the 3rd tier is not acceptable, or you are working with very high motion content, one can lower the resolution and bitrate combination further.

Following table provides a possible bit rate recommendations for AIV.

1.26. For VOD content, the average segment bit rate MUST be within 10% of the AVERAGE-BANDWIDTH attribute. (See Declared versus measured values of bandwidths.)

1.27. For VOD content, the measured peak bit rate MUST be within 10% of the BANDWIDTH attribute.

1.28. For live (linear) content, the average segment bit rate over a long (~1 hour) period of time MUST be less than 110% of the AVERAGE-BANDWIDTH attribute.

1.29. For live (linear) content, the measured peak bit rate MUST be less than 125% of the BANDWIDTH attribute.

1.30. For VOD content, the peak bit rate SHOULD be no more than 200% of the average bit rate.

1.31. Different variants MAY have different frame rates.

1.32. * The default video variants SHOULD be the 2000 kbit/s (average bit rate) variant. (Defaults are the first variant listed in the Multivariant Playlist within a group of variants having compatible audio).

1.33. All video variants SHOULD have identical aspect ratios.

1.34. For maximum compatibility when UHD video resolution is provided, some UHD variants SHOULD be less than or equal to 15 Mbit/s.

1.35. For HDR10 content, the Mastering Display Color Volume and Content Light Level Information SEI messages SHOULD be present.

1.36. MV-HEVC video MUST NOT be used for anything other than stereo video.

1.37. Level for AV1 MUST be less than or equal to Level 6.2

1.38. All APMP monoscopic videos MUST be encoded using HEVC/H.265.

1.39. The container format for AV1 video MUST be fMP4.

Audio

2. Audio encoding requirements

2.1. Audio data SHOULD be provided as an elementary audio stream or in fMP4.

2.2. Codecs that provide stereo audio are:

• Apple Positional Audio Codec (APAC)

• AAC-LC

• HE-AAC v1

• HE-AAC v2

• xHE-AAC

• Apple Lossless

• FLAC

2.3. * Stereo audio in AAC, HE-AAC v1, or HE-AAC v2 format MUST be provided.

2.4. You SHOULD NOT use HE-AAC if your audio bit rate is above 64 kbit/s.

2.5. Supported multichannel audio codecs are:

• APAC

• AAC-LC

• HE-AAC v1

• Apple Lossless

• FLAC

• Dolby Digital (AC-3)

• Dolby Digital Plus (E-AC-3)(ec-3)

• Dolby Digital Plus JOC (ec+3)

(See Values for the CODECS attribute for more information about specifying Dolby Digital Plus JOC.)

2.6. * If Dolby Digital Plus is provided and your streams are delivered to devices that don’t support Dolby Digital Plus, then Dolby Digital MUST be provided also. See Audio compatibility.

2.7. Stereo audio MAY be provided at multiple bit rates.

2.8. * Multichannel audio using a particular codec MAY be provided at multiple bit rates.

2.9. Overall bit rate recommendations are as follows:

Bitrate recommendations for stereo are as follows:

Bitrate recommendations for multi-channel surround formats are as follows:

Bitrate recommendations for Ambisonics are as follows:

See APAC for more information about ambisonics.

2.10. * You MAY change channel layout within a stream.

2.11. Channel layout changes MUST be in conjunction with an EXT-X-DISCONTINUITY tag.

2.12. If you provide Descriptive Video Service (DVS), also called “Audio Description”, it MUST be marked with the attribute CHARACTERISTICS="public.accessibility.describes-video".

2.13. If you provide DVS, the AUTOSELECT attribute MUST have a value of “YES".

2.14. The name of DVS audio SHOULD indicate that the stream is DVS content.

2.15. If you provide alternative audio or DVS, you MUST provide it for the entire content duration, even if it only really exists for a portion of the main content.

2.16. Alternative audio or DVS MAY reuse the audio segments of regular content when the alternative content isn’t available.

2.17. A single Media Segment MUST NOT contain multiple audio streams.

2.18. Loudness management or Dynamic range control SHOULD be present unless all content (including ads) has been encoded at the same audio levels.

2.19. In fMP4 files, except for the APAC codec, you SHOULD provide loudness information by way of a loudness box (’ludt’). When present, the loudness box takes precedence over any loudness information in the audio stream. For APAC, a loudness box SHALL not be used.

2.20. In the absence of a loudness box, Dolby Digital and Dolby Digital Plus loudness SHOULD be specified by the dialnorm field (ATSC A/52:2012). 

2.21. For AAC, in the absence of a loudness box, AAC dialog loudness SHOULD be specified by either AAC prog_ref_level (ISO 14496-3 subclause 4.5.2.7), as specified by SCTE 193-1 section 7.4.1, or by the loudnessInfo() payload as specified by ISO 23003-4, in which case, samplePeakLevel or truePeakLevel MUST be present, measurementSystem MUST be 2, and methodDefinition MUST be 1 or 2, while for video content it SHOULD be 2.

2.22. For xHE-AAC, loudness metadata MUST be present according to the Basic Loudness Metadata specified in ISO 23003-4 Table I.5; samplePeakLevel or truePeakLevel MUST be present. The methodDefinition SHOULD be 2 for video content.

2.23. The loudness value MUST indicate the actual loudness of the content.

2.24. HE-AAC in fMP4 files MUST use explicit signaling of SBR data.

2.25. The container format for xHE-AAC, Apple Lossless, FLAC, and APAC audio MUST be fMP4.

2.26. If you provide non-Dolby multichannel audio, you SHOULD provide multichannel AAC also.

2.27. For audio description, the LANGUAGE attribute MUST be present and indicate the primary language used to convey the descriptions.

2.28. Audio that has been prepared or otherwise processed to heighten the intelligibility of speech MAY be marked with the attribute CHARACTERISTICS="public.accessibility.enhances-speech-intelligibility".

2.29. Supported multi-format audio codecs that carry the combination of two or more formats out of channels, objects and Ambisonics are:

• APAC

• Dolby Digital Plus JOC

2.30. APAC encoded content MUST have in-stream loudness and DRC metadata.

2.31. If you provide APAC immersive audio, you SHOULD provide stereo AAC also.

Ads and pre-/mid-/post-rolls

3. Ad requirements (See also the Media Playlists section of HTTP Live Streaming (HLS) authoring specification for Apple devices.)

3.1. Your ads and other nonprimary media MAY be inserted in the Media Playlists or as Interstitials.

3.2. Inserted media SHOULD be encoded with the same codecs as the other content in the Media Playlist.

3.3. Inserted media SHOULD be encoded with the same aspect ratio as the other content in the Media Playlist.

3.4. Inserted media SHOULD be at or under the specified bandwidths for that variant.

Accessibility

4. Accessibility requirements

4.1. Captions SHOULD be provided with your streams to make content accessible to people who are deaf or hard of hearing.

4.2. Supported caption formats are:

• CEA-608 closed captions

• CEA-708 closed captions

• WebVTT subtitles

• IMSC1 subtitles (text profile only)

4.3. Closed captions (if any) MUST be included in the video Media Segments.

4.4. The presence of closed captions MUST be declared via an EXT-X-MEDIA tag that contains a LANGUAGE attribute.

4.5. If a subtitles track is intended to provide accessibility for people who are deaf or hard of hearing, it MUST be marked with the attribute CHARACTERISTICS="public.accessibility.transcribes-spoken-dialog,public.accessibility.describes-music-and-sound". (Subtitles with this attribute value are treated the same as closed captions.)

4.6. If a subtitles track is intended to provide accessibility for people who are deaf or hard of hearing, the AUTOSELECT attribute MUST have a value of "YES".

4.7. The LANGUAGE attribute MUST be included in the EXT-X-MEDIA tag for a subtitles track.

4.8. For information on including audio descriptions with your streams, see items 2.12 through 2.16.

Subtitles

5. Subtitle requirements

5.1. Subtitles MAY be provided.

5.2. * Subtitles MUST be WebVTT (according to the HLS specification) or IMSC1 in fMP4.

5.3. WebVTT subtitles MUST be in text files, with an X-TIMESTAMP-MAP according to the HLS specification.

5.4. IMSC1 subtitles MUST be in fMP4 files.

5.5. The subtitle playlist MUST exist for the entirety of the main content, even if the actual subtitles only exist for a portion of the content.

5.6. For live (linear) content, target durations for subtitle playlists MUST be identical to other media.

5.7. For VOD content, target durations of subtitle playlists MAY be longer than the other media.

5.8. If the content has forced subtitles and regular subtitles in a given language, the regular subtitles track in that language MUST contain both the forced subtitles and the regular subtitles for that language.

5.9. If your videos contain text burnt into the video and you have access to a version without the burn-in, you SHOULD use forced subtitles instead. (This allows you to easily translate into multiple languages. An example of when you might use forced subtitles is a science fiction film, where alien languages are translated into English.)

5.10. The kind of subtitles SHOULD be specified in the CODECS attribute of the associated EXT-X-STREAM-INF tags. You SHOULD use "stpp.ttml.im1t" to identify IMSC1 subtitles. You MAY use "wvtt" to identify WebVTT subtitles.

5.11. Forced subtitles SHOULD always have AUTOSELECT=YES.

Trick Play

6. Trick play requirements

6.1. I-frame playlists (EXT-X-I-FRAME-STREAM-INF) MUST be provided to support scrubbing and scanning UI.

6.2. You SHOULD have one frame per second dense I-frame renditions. These are dedicated renditions that only contain I-frames.

6.3. Alternatively, you MAY use the I-frames from your normal content, but trick play performance is improved with a higher density of I-frames.

6.4. If you provide multiple bit rates at the same spatial resolution for your regular video, you SHOULD create the I-frame playlist for that resolution from the same source used for the lowest bit rate in that group.

6.5. The bit rate of I-frame playlists SHOULD be the bit rate of a normal playlist of the same resolution times the fps of the I-frame playlist divided by eight. (See I-frame bit rates versus normal bit rates.)

6.6. * You SHOULD provide multiple I-frame Media Playlists with different bit rates.

6.7. As with normal video, there are many possible choices of bit rates for dense I-frame variants. The following tables provide one possible set of variants. (See On bit rates for variants.)

6.8. I-frame playlists MUST contain the EXT-X-I-FRAMES-ONLY tag.

6.9. The peak segment bit rate MUST be calculated according to the HLS specification.

6.10. If using fMP4, I-frame segments MUST include the ‘moof’ header associated with the I-frame.

6.11. For live (linear) content, target durations for I-frame playlists MUST be identical to other media.

6.12. For VOD content, target durations of I-frame playlists MAY be different from the other media.

6.13. * I-frame playlists MAY use a different video codec than the normal video segments.

6.14. * For backward compatibility, some trick play content SHOULD be encoded with H.264.

6.15. If HDR trick play streams are provided, they SHOULD be provided at all resolutions.

6.16. * For backward compatibility, SDR trick play streams MUST be provided.

6.17. I-frame content MAY be encoded using the fMP4 ‘mjpg’ codec. (See I-frame image sequences.)

Media Segmentation

7. Media segmentation requirements

7.1. Your media MUST be continuous across segments, with the exception of transitions for ads and other inserted material.

7.2. If using a transport stream, continuity counters and timestamps MUST be sequential.

7.3. If using fMP4, the track fragment decode time MUST be consistent with the decode time and duration of the previous segment.

7.4. Video segments MUST start with an IDR frame.

7.5. Target durations SHOULD be 6 seconds.

7.6. Segment durations SHOULD be nominally 6 seconds (for example, NTSC 29.97 may be 6.006 seconds).

7.7. Media Segments MUST NOT exceed the target duration by more than 0.5 seconds.

7.8. Each xHE-AAC segment SHOULD start with an Immediate Playout Frame (IPF).

7.9. Each APAC segment MUST start with an Audio Synchronization Packet (ASP).

Media Playlists

8. Media Playlist requirements

8.1. You MUST use sufficiently accurate segment durations to ensure that the sum of the EXTINF durations of any contiguous group of segments is within one video frame duration of the actual duration of the content.

8.2. Audio and video playlists MUST all use the same target duration.

8.3. Audio and video playlists MUST contain the same duration of the content.

8.4. The EXT-X-PROGRAM-DATE-TIME tag MUST be present in every live (linear) Media Playlist.

8.5. The date-time value of an EXT-X-PROGRAM-DATE-TIME tag SHOULD be aligned with the airtime of the content.

8.6. If your Media Playlists are created from static source content (VOD), you MUST add the EXT-X-PLAYLIST-TYPE with the value VOD.

8.7. Within one asset, all Media Playlists with an EXT-X-PLAYLIST-TYPE of VOD MUST cover exactly the same media time range.

8.8. If your Media Playlists are event style (start from a fixed point with segments never removed), you MUST add the EXT-X-PLAYLIST-TYPE with the value EVENT.

8.9. Separate audio streams MUST be declared using EXT-X-MEDIA tags.

8.10. The LANGUAGE attribute MUST be included in every EXT-X-MEDIA tag that doesn’t have TYPE=VIDEO.

8.11. You MUST provide at least six segments in a live (linear) playlist.

8.12. * You SHOULD provide at least 15 minutes of content in a live (linear) playlist.

8.13. Breaks of encoding continuity MUST be indicated with the EXT-X-DISCONTINUITY tag.

8.14. Video frame rate changes MUST be marked as a discontinuity using EXT-X-DISCONTINUITY tags.

8.15. All variants and renditions MUST have discontinuities at the same points in time.

8.16. * You SHOULD avoid switching codecs at discontinuities, for example, switching between HEVC and H.264, or between AAC and Dolby Digital.

8.17. If live (linear) content will ever contain an EXT-X-DISCONTINUITY tag, the EXT-X-DISCONTINUITY-SEQUENCE tag MUST always be present.

8.18. Your media requests MUST NOT use HTTP redirects, with the exception of ad content to allow dynamic selection of ads.

8.19. You SHOULD identify interstitial and program boundaries using the EXT-X-DATERANGE tag.

8.20. If using fMP4, EXT-X-MAP tags MUST be present.

8.21. Metadata SHOULD be in the playlist (using EXT-X-DATERANGE) rather than in the media (using Timed Metadata).

8.22. * For maximum interoperability, all audio/video variants and renditions SHOULD have segment boundaries at the same points in time.

8.23. If your xHE-AAC segments start with an IPF, you SHOULD use the EXT-X-INDEPENDENT-SEGMENTS tag in the Media Playlist.

8.24. A live (linear) playlist update SHOULD be considered invalid when the Last-Modified HTTP header, if supplied, is more than three target durations from the Date HTTP header.

8.25. If your APAC segments start with an ASP, you SHOULD use the EXT-X-INDEPENDENT-SEGMENTS tag in the Media Playlist.

Multivariant Playlist

9. Multivariant Playlist requirements

9.1. Your EXT-X-STREAM-INF tag MUST always provide the CODECS attribute.

9.2. Your EXT-X-STREAM-INF tag MUST always provide the RESOLUTION attribute if the rendition includes video.

9.3. Your EXT-X-I-FRAME-STREAM-INF tag MUST always provide the CODECS attribute.

9.4. Your EXT-X-I-FRAME-STREAM-INF tag MUST always provide the RESOLUTION attribute.

9.5. You SHOULD deliver video and audio as separate streams.

9.6. If you have multichannel audio, you MUST use separate audio streams.

9.7. If you have alternative audio content (languages/commentary/DVS), you MUST use separate audio streams.

9.8. If you have different video angles, you MUST use separate audio streams.

9.9. You MUST provide multiple bit rates of video (that is, variants).

9.10. For HD content, there SHOULD be at least two variants encoded at the highest-available resolution.

9.11. If your video segments start with an IDR, you SHOULD use the EXT-X-INDEPENDENT-SEGMENTS tag in the Multivariant Playlist. (See item 7.4.)

9.12. If your video segments start with an IDR and the EXT-X-INDEPENDENT-SEGMENTS tag isn’t in the Multivariant Playlist, you MUST use the EXT-X-INDEPENDENT-SEGMENTS tag in all video Media Playlists. (See item 7.4.)

9.13. The BANDWIDTH attribute MUST be the largest sum of peak segment bit rates that’s produced by any playable combination of renditions.

9.14. You MUST include the AVERAGE-BANDWIDTH attribute.

9.15. Each EXT-X-STREAM-INF tag that includes video content MUST have a FRAME-RATE attribute.

9.16. The VIDEO-RANGE attribute MUST be specified unless all variants and renditions are SDR.

9.17. Within a group of Renditions (EXT-X-MEDIA tags having the same TYPE and GROUP-ID), those tags having the same LANGUAGE value should be ordered from most general to most specific. (Because CHARACTERISTICS are open-ended, the matching algorithm needs the ordering since it can’t interpret all the semantics.)

9.18. An EXT-X-CONTENT-STEERING tag SHOULD always have a PATHWAY-ID attribute.

9.19. The SCORE attribute (if present) MUST be on every variant. Otherwise, the SCORE attribute will be ignored.

9.20. For APAC, the APAC profile and level MUST be provided as a part of Codec string. See APAC for more information about APAC profile and level.

Delivery

10. Delivery requirements

10.1. The server MUST deliver playlists using gzip content-encoding.

10.2. You SHOULD support stream failover, for example by listing duplicate streams in the Multivariant Playlist.

10.3. Media data SHOULD NOT be delivered to the application through a local server.

10.4. You SHOULD use the recommended MIME types for content. The recommendations are in the following table:

Privacy

11. Privacy requirements

11.1. Multivariant Playlists SHOULD be delivered using Transport Layer Security (TLS).

11.2. Media Playlists SHOULD be delivered using TLS.

11.3. Media Segments SHOULD be delivered using TLS.

11.4. Media Segment URLs requested over unencrypted transport SHOULD NOT contain revealing strings, such as movie title, show title, episode name, episode number, genre, advertiser, or product.

Security

12. Security requirements

12.1. Transport Layer Security (TLS) MUST be version 1.2 or later with forward secrecy.

12.2. TLS MUST NOT use known-insecure cryptographic primitives (such as, RC4 encryption, SHA-1 certificate signatures).

12.3. Within TLS, key sizes MUST be 2048 bits for RSA and 256 bits for EC.

12.4. The URLs for Media Segments SHOULD NOT be completely static. URLs should be issued per device or changed over time.

Content Protection

13. Content protection requirements

13.1. Content protection of video and audio SHOULD follow the FairPlay Streaming (FPS) specification.

13.2. If the content is encrypted with FPS, the method MUST be SAMPLE-AES.

13.3. If the content is encrypted with FPS, the key format MUST be "com.apple.streamingkeydelivery".

13.4. The IV attribute SHOULD NOT be used with FPS unless necessary for interoperability.

13.5. Content with HD resolutions SHOULD use HDCP-LEVEL of TYPE-0.

13.6. Content with greater than HD resolutions SHOULD use HDCP-LEVEL of TYPE-1.

13.7. Video encrypted with Common Encryption MUST use an encrypt:skip pattern of 1:9 (10% partial encryption).

13.8. Content encrypted with FPS MAY use the ALLOWED-CPC attribute. (See ALLOWED-CPC values for FairPlay Streaming.)

13.9. Common encryption MUST NOT use content sensitive encryption.

13.10. Content authors MAY mix encrypted and unencrypted samples in a single HLS fMP4 segment with a single Media Initialization Section by supplying both an encrypted SampleDescription at index 0 and an unencrypted SampleDescription at index 1 for each track. The sample index field of each sample should point to the appropriate SampleDescription.

13.11. Encryption with SAMPLE-AES-CTR SHALL NOT be used on Apple devices.

Low-Latency HLS

14. Low-Latency HLS requirements

14.1. Low-Latency stream delivery MUST meet all requirements of the Low-Latency Server Configuration Profile in Appendix B of draft-pantos-hls-rfc8216bis-07 or later.

14.2.

14.2a. The Part Target Duration MUST be at least the maximum round-trip time (RTT) to the server that 95% of the clients are expected to see (P95 RTT).

14.2b. The Part Target Duration SHOULD be at least three times the P95 RTT.

14.2c. The RECOMMENDED Part Target Duration is one second.

14.3. The PART-HOLD-BACK value MUST be at least three times the Part Target Duration.

14.4. Services with Playlist windows longer than two minutes SHOULD offer Playlist Delta Updates.

14.5. Services that offer Playlist Delta Updates and use EXT-X-DATERANGE tags SHOULD also use CAN-SKIP-DATERANGES=YES.

SharePlay

15. SharePlay HLS requirements

15.1. For live (linear) content, the timeline derived from the EXT-X-PROGRAM-DATE-TIME tag is used for synchronization. That timeline MUST be in agreement for all participants.

15.2. For VOD content, the timeline based on the start of the playlist is used for synchronization. That timeline MUST be in agreement for all participants.

15.3. Interstitials delivered to participants in a SharePlay session SHOULD match in duration. If they do not, participants receiving longer duration interstitials will miss some of the primary content. This behavior can only be overridden when all participants are using apps that support control of coordinated media playback.

Spatial (stereo, immersive and projected) video

16. Spatial (stereo, immersive and projected) video requirements

16.1. All variants containing spatial video MUST be marked with a REQ-VIDEO-LAYOUT attribute.

16.2. All spatial video content MUST include Video Extended Usage ('vexu') atoms/boxes. (See Additional spatial video specifications.)

16.3. Switches between spatial and non-spatial video content MUST be marked with an EXT-X-DISCONTINUITY tag, or the Media Initialization Section MUST contain sample descriptions for both kinds of content.

16.4. Stereo and Immersive video content SHOULD include parallax metadata if your content has subtitles. (See Additional spatial video specifications.)

16.5. If spatial video content includes sections of monoscopic video content, then the REQ-VIDEO-LAYOUT attribute MUST include “CH-MONO” as one entry.

Amended requirements for macOS

All general rules apply except as expressly modified by a rule with the same number in this section. Rules with a leading plus sign (+) are additional rules.

Video

1. Video encoding requirements

1.3.

1.3b. Profile and Level for H.264 MUST be less than or equal to High Profile, Level 5.0.

Amended requirements for iOS

All general rules apply except as expressly modified by a rule with the same number in this section. Rules with a leading plus sign (+) are additional rules.

Video

1. Video encoding requirements

1.6.

1.6b. Profile and Level for H.264 MUST be less than or equal to High Profile, Level 6.0.

1.9.

1.9a. Profile and Level for Dolby Vision MUST be Profile 5 (single layer 10-bit HEVC) or Profile 10 (single layer 10-bit AV1) and less than or equal to Level 9.

1.9b. + For maximum compatibility, some Dolby Vision variants SHOULD be Profile 5 and less than or equal to Level 7.

1.32.

1.32a. For Wi-Fi delivery, the default video variant SHOULD be the 2000 kbit/s (average bit rate) variant.

1.32b. For cellular delivery, the default video variant SHOULD be the 730 kbit/s (average bit rate) variant.

Multivariant Playlist

9. Multivariant Playlist requirements

9.21. + Multivariant Playlists that are delivered over cellular networks MUST contain a variant whose peak BANDWIDTH is less than or equal to 192 kbit/s.

9.22. + For backward compatibility, a peak 192 kbit/s H.264 variant packaged in a transport stream SHOULD be provided for cellular.

Amended requirements for visionOS

All general rules apply except as expressly modified by a rule with the same number in this section. Rules with a leading plus sign (+) are additional rules.

The following general rules regarding compatibility aren’t applicable in visionOS if all variants contain stereo video content: 1.3a, 1.6a, 1.9b, 1.12, 1.24, 2.3, 2.6, 6.14, 6.16.

Video

1. Video encoding requirements

1.9.

1.9a. Dolby Vision monoscopic content MUST be Profile 5 (single layer 10-bit HEVC) and less than or equal to Level 9.

1.9c. + Dolby Vision stereo video MUST be Profile 20 (MV-HEVC) and less than or equal to Level 9.

1.25. Suggested bit rates for MV-HEVC variants.

1.40. + Stereo video MUST be encoded using Dolby Vision Profile 20 (MV-HEVC).

Trick play

6. Trick play requirements

6.6. If your only content is stereo video, then you SHOULD provide only one I-frame Media Playlist. (See item 6.19.)

6.18. + Trick play content SHOULD be monoscopic and rectilinear.

6.19. + In visionOS, a thumbnail list is produced for scrubbing and scanning. These thumbnails are 160px height with a width that matches the aspect ratio of the main content. For better performance, you MAY provide an I-frame playlist having exactly this height.

Spatial (stereo, immersive and projected) video

16. Spatial (stereo, immersive and projected) video requirements

16.6. + All Stereo (including APMP) video MUST be encoded using MV-HEVC.

16.7. + Immersive video content MUST use CH-STEREO and PROJ-AIV for channel and projection specifier in REQ-VIDEO-LAYOUT.

Amended requirements for tvOS

All general rules apply except as expressly modified by a rule with the same number in this section. Rules with a leading plus sign (+) are additional rules.

Video

1. Video encoding requirements

1.3.

1.3b. Profile and Level for H.264 MUST be less than or equal to High Profile, Level 5.1.

1.20. For HDR content, frame rates less than or equal to 30 fps MUST be provided.

1.25. The 145 kbit/s variant SHOULD NOT be provided.

Audio

2. Audio encoding requirements

2.8. Multichannel audio using a particular codec MAY be provided at multiple bit rates. However, Dolby Atmos content SHOULD be restricted to a single bit rate.

Trick Play

6. Trick play requirements

6.16. SDR trick play streams MUST be provided.

Media Playlists

8. Media Playlist requirements

8.12. You SHOULD provide at least 120 minutes of content in a live (linear) playlist.

Multivariant Playlist

9. Multivariant Playlist requirements

9.20. + You MUST have no audio-only variants listed in the Multivariant Playlist.

Amended requirements for AirPlay 2-Enabled TVs

All general rules apply except as expressly modified by a rule with the same number in this section. Rules with a leading plus sign (+) are additional rules.

Video

1. Video encoding requirements

1.23. If multiple video streams are provided (H.264, HEVC, HDR), each stream MUST provide all anticipated bandwidths.

1.41. + Encrypted fMP4 content MUST contain either a Sample Encryption Box ('senc'), or both a Sample Auxiliary Information Sizes Box ('saiz') and a Sample Auxiliary Information Offsets Box ('saio').

Audio

2. Audio encoding requirements

2.10. Channel layout SHOULD NOT change within a stream.

Ads and pre-/mid-/post-rolls

3. Ad requirements

3.5. + Inserted media SHOULD be at a similar frame rate (x, 2x, x/2) as the other content in the Media Playlist.

Subtitles

5. Subtitle requirements

5.2. Subtitles MUST be WebVTT.

Trick Play

6. Trick play requirements

6.13. If a normal video variant uses a video codec, one or more I-frame variants MUST exist with the same video codec or the mjpg codec.

Media Playlists

8. Media Playlist requirements

8.16. You SHOULD NOT switch codecs at discontinuities. For example, don’t switch between HEVC and H.264, or between AAC and Dolby Digital.

8.22. All video variants and renditions MUST have segment boundaries at the same points in time.

8.25. + Frame rate changes at discontinuities SHOULD use a similar frame rate (x, 2x, x/2).

Multivariant Playlist

9. Multivariant Playlist requirements

9.23. + You SHOULD provide a full range of variants for each codec type and frame rate. Similar frame rates (x, 2x, x/2) are compatible, nonsimilar frame rates may cause playback issues.

9.24. + If you supply HDR content, you SHOULD provide both Dolby Vision and HDR10.

Revision history

The following table describes the changes to this document.

Topics

Appendixes

• HTTP Live Streaming (HLS) Authoring Specification for Apple devices appendixes

See Also

Specifications and other documents

• Using content protection systems with HLS
• About the Common Media Application Format with HTTP Live Streaming (HLS)
• Enabling Low-Latency HTTP Live Streaming (HLS)
• Links to additional specifications and videos
• Videos about HLS
• Providing metadata for xHE-AAC video soundtracks
• Adjusting anchor loudness
• Providing JavaScript Object Notation (JSON) chapters