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fix documentation

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Luro02 2020-02-10 13:51:37 +01:00
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101
src/tags/master_playlist/variant_stream.rs
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@ -8,71 +8,71 @@ use crate::types::{ClosedCaptions, ProtocolVersion, StreamData, UFloat};
use crate::utils::{quote, tag, unquote};
use crate::Error;
/// A server MAY offer multiple Media Playlist files to provide different
/// encodings of the same presentation. If it does so, it SHOULD provide
/// a Master Playlist file that lists each Variant Stream to allow
/// A server may offer multiple [`MediaPlaylist`] files to provide different
/// encodings of the same presentation. If it does so, it should provide
/// a [`MasterPlaylist`] that lists each [`VariantStream`] to allow
/// clients to switch between encodings dynamically.
///
/// Master Playlists describe regular Variant Streams with EXT-X-STREAM-
/// INF tags and I-frame Variant Streams with EXT-X-I-FRAME-STREAM-INF
/// tags.
/// The server must meet the following constraints when producing
/// [`VariantStream`]s in order to allow clients to switch between them
/// seamlessly:
///
/// If an EXT-X-STREAM-INF tag or EXT-X-I-FRAME-STREAM-INF tag contains
/// the CODECS attribute, the attribute value MUST include every media
/// format [RFC6381] present in any Media Segment in any of the
/// Renditions specified by the Variant Stream.
/// - Each [`VariantStream`] must present the same content.
///
/// The server MUST meet the following constraints when producing Variant
/// Streams in order to allow clients to switch between them seamlessly:
/// - Matching content in [`VariantStream`]s must have matching timestamps. This
/// allows clients to synchronize the media.
///
/// o Each Variant Stream MUST present the same content.
/// - Matching content in [`VariantStream`]s must have matching
/// [`ExtXDiscontinuitySequence`].
///
/// - Each [`MediaPlaylist`] in each [`VariantStream`] must have the same target
/// duration. The only exceptions are subtitle renditions and
/// [`MediaPlaylist`]s containing an [`ExtXIFramesOnly`] tag, which may have
/// different target durations if they have [`ExtXPlaylistType::Vod`].
///
/// o Matching content in Variant Streams MUST have matching timestamps.
/// This allows clients to synchronize the media.
/// - Content that appears in a [`MediaPlaylist`] of one [`VariantStream`] but
/// not in another must appear either at the beginning or at the end of the
/// [`MediaPlaylist`] and must not be longer than the target duration.
///
/// o Matching content in Variant Streams MUST have matching
/// Discontinuity Sequence Numbers (see Section 4.3.3.3).
/// - If any [`MediaPlaylist`]s have an [`ExtXPlaylistType`] tag, all
/// [`MediaPlaylist`]s must have an [`ExtXPlaylistType`] tag with the same
/// value.
///
/// o Each Media Playlist in each Variant Stream MUST have the same
/// target duration. The only exceptions are SUBTITLES Renditions and
/// Media Playlists containing an EXT-X-I-FRAMES-ONLY tag, which MAY
/// have different target durations if they have an EXT-X-PLAYLIST-
/// TYPE of VOD.
/// - If the Playlist contains an [`ExtXPlaylistType`] tag with the value of
/// VOD, the first segment of every [`MediaPlaylist`] in every
/// [`VariantStream`] must start at the same media timestamp.
///
/// o Content that appears in a Media Playlist of one Variant Stream but
/// not in another MUST appear either at the beginning or at the end
/// of the Media Playlist file and MUST NOT be longer than the target
/// duration.
/// - If any [`MediaPlaylist`] in a [`MasterPlaylist`] contains an
/// [`ExtXProgramDateTime`] tag, then all [`MediaPlaylist`]s in that
/// [`MasterPlaylist`] must contain [`ExtXProgramDateTime`] tags with
/// consistent mappings of date and time to media timestamps.
///
/// o If any Media Playlists have an EXT-X-PLAYLIST-TYPE tag, all Media
/// Playlists MUST have an EXT-X-PLAYLIST-TYPE tag with the same
/// value.
/// - Each [`VariantStream`] must contain the same set of Date Ranges, each one
/// identified by an [`ExtXDateRange`] tag(s) with the same ID attribute value
/// and containing the same set of attribute/value pairs.
///
/// o If the Playlist contains an EXT-X-PLAYLIST-TYPE tag with the value
/// of VOD, the first segment of every Media Playlist in every Variant
/// Stream MUST start at the same media timestamp.
///
/// o If any Media Playlist in a Master Playlist contains an EXT-X-
/// PROGRAM-DATE-TIME tag, then all Media Playlists in that Master
/// Playlist MUST contain EXT-X-PROGRAM-DATE-TIME tags with consistent
/// mappings of date and time to media timestamps.
///
/// o Each Variant Stream MUST contain the same set of Date Ranges, each
/// one identified by an EXT-X-DATERANGE tag(s) with the same ID
/// attribute value and containing the same set of attribute/value
/// pairs.
///
/// In addition, for broadest compatibility, Variant Streams SHOULD
/// contain the same encoded audio bitstream. This allows clients to
/// switch between Variant Streams without audible glitching.
///
/// The rules for Variant Streams also apply to alternative Renditions
/// (see Section 4.3.4.2.1).
/// In addition, for broadest compatibility, [`VariantStream`]s should
/// contain the same encoded audio bitstream. This allows clients to
/// switch between [`VariantStream`]s without audible glitching.
///
/// [RFC6381]: https://tools.ietf.org/html/rfc6381
/// [`ExtXDiscontinuitySequence`]: crate::tags::ExtXDiscontinuitySequence
/// [`ExtXPlaylistType::Vod`]: crate::tags::ExtXPlaylistType::Vod
/// [`MediaPlaylist`]: crate::MediaPlaylist
/// [`MasterPlaylist`]: crate::MasterPlaylist
/// [`ExtXDateRange`]: crate::tags::ExtXDateRange
/// [`ExtXProgramDateTime`]: crate::tags::ExtXProgramDateTime
/// [`ExtXPlaylistType`]: crate::tags::ExtXPlaylistType
/// [`ExtXIFramesOnly`]: crate::tags::ExtXIFramesOnly
#[derive(Debug, Clone, PartialEq, PartialOrd)]
pub enum VariantStream {
/// The [`VariantStream::ExtXIFrame`] variant identifies a [`MediaPlaylist`]
/// file containing the I-frames of a multimedia presentation.
/// It stands alone, in that it does not apply to a particular URI in the
/// [`MasterPlaylist`].
///
/// [`MasterPlaylist`]: crate::MasterPlaylist
/// [`MediaPlaylist`]: crate::MediaPlaylist
ExtXIFrame {
/// The URI identifies the I-frame [`MediaPlaylist`] file.
/// That Playlist file must contain an [`ExtXIFramesOnly`] tag.
@ -82,6 +82,7 @@ pub enum VariantStream {
/// This field is required.
///
/// [`MediaPlaylist`]: crate::MediaPlaylist
/// [`ExtXIFramesOnly`]: crate::tags::ExtXIFramesOnly
uri: String,
/// Some fields are shared between [`VariantStream::ExtXStreamInf`] and
/// [`VariantStream::ExtXIFrame`].
@ -91,6 +92,8 @@ pub enum VariantStream {
/// This field is optional.
stream_data: StreamData,
},
/// [`VariantStream::ExtXStreamInf`] specifies a [`VariantStream`], which is
/// a set of renditions that can be combined to play the presentation.
ExtXStreamInf {
/// The URI specifies a [`MediaPlaylist`] that carries a rendition of
/// the [`VariantStream`]. Clients that do not support multiple video