HLS Generation

HLS Generation¶

GPAC can be used to generate HLS rather than MPEG-DASH manifest formats, and can also be used to generate the two manifests in one pass.
The guidelines on segmentation are the same as with general dashing, please refer to the rest of the wiki for more info on this.
HLS generation is supported by both MP4Box and gpac.

HLS with one file per segment¶

Generating an HLS with one file per media segment is equivalent to dashing under the live profile.

MP4Box -dash 1000 -profile live -out res/live.m3u8 source1 source2 
gpac -i source1 -i source2 -o res/live.m3u8:profile=live

This will by default generate ISOBMFF / fmp4 files. To generate MPEG-2 TS files, use:
gpac -i source1 -i source2 -o res/live.m3u8:profile=live:muxtype=ts

Note that gpac will by default generate non-multiplexed outputs. To generate a multiplexed file, you need to flag inputs as belonging to the same quality , or Representation in DASH terminology:
gpac -i video:#Representation=main -i audio:#Representation=main -o res/live.m3u8:profile=live:muxtype=ts

HLS with a single file for all segments¶

Generating an HLS with one file per quality is equivalent to dashing under the onDemand profile.

gpac -i source1 -i source2 -o res/live.m3u8:profile=onDemand

Specifying manifest names¶

The child playlist names are by default the manifest (master playlist) radical suffixed with _1, _2 ...
This can be changed by using the PID property HLSPL :

gpac -i source1:#HLSPL=video.m3u8 -i source2:#HLSPL=audio.m3u8 -o res/live.m3u8

This will generate live.m3u8, video.m3u8 and audio.m3u8

Renditions¶

Grouping¶

When several renditions are possible for a set of inputs, the default behavior is as follows:

if video is present, it is used as the main content
otherwise, audio is used as the main content

The main content is repeated for each combination with other content. For example with 1 video and 3 audios, you will have:

#EXT-X-STREAM-INF:BANDWIDTH=1000000,CODECS="avc1.42C01F,mp4a.40.2",RESOLUTION=1280x720,FRAME-RATE="25",AUDIO="audio1"
video.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=1000000,CODECS="avc1.42C01F,mp4a.40.2",RESOLUTION=1280x720,FRAME-RATE="25",AUDIO="audio2"
video.m3u8

#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio1",NAME="1",LANGUAGE="fra",AUTOSELECT=YES,URI="audio_1.m3u8",CHANNELS="1"
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio2",NAME="2",LANGUAGE="eng",AUTOSELECT=YES,URI="audio_2.m3u8",CHANNELS="1"

This behavior can be changed by specifying a group for input streams using the PID property HLSGroup :
gpac -i source1 -i audio1:#HLSGroup=MyAudio -i audio2:#HLSGroup=MyAudio -o res/live.m3u8

This will result in:

##EXT-X-STREAM-INF:BANDWIDTH=1000000,CODECS="avc1.42C01F,mp4a.40.2",RESOLUTION=1280x720,FRAME-RATE="25",AUDIO="MyAudio"
video.m3u8

##EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="MyAudio",NAME="1",LANGUAGE="fra",AUTOSELECT=YES,URI="audio_1.m3u8",CHANNELS="1"
##EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="MyAudio",NAME="2",LANGUAGE="eng",AUTOSELECT=YES,URI="audio_2.m3u8",CHANNELS="1"

Warning
GPAC will not check if streams within a group have the same codec properties, you must only put in the same group streams with the same coding configurations, i.e. streams for which the CODECS parameter is the same.

Naming¶

The component names are the DASH representation ID. By default this is an integer value, but it can be set to whatever suits you:

gpac -i source1 -i audio1:#HLSGroup=MyAudio:#Representation=Soustitres -i audio2:#HLSGroup=MyAudio:#Representation=Subtitles -o res/live.m3u8

This will result in:

#EXT-X-STREAM-INF:BANDWIDTH=1000000,CODECS="avc1.42C01F,mp4a.40.2",RESOLUTION=1280x720,FRAME-RATE="25",AUDIO="MyAudio"
video.m3u8

#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="MyAudio",NAME="Soustitres",LANGUAGE="fra",AUTOSELECT=YES,URI="audio_1.m3u8",CHANNELS="1"
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="MyAudio",NAME="Subtitles",LANGUAGE="eng",AUTOSELECT=YES,URI="audio_2.m3u8",CHANNELS="1"

Dual DASH + HLS Generation¶

GPAC can generate a manifest for both HLS and DASH by using the dual option.

gpac -i source1 -i source2 -o res/live.mpd:dual:profile=live

This will generate live.mpdand live.m3u8 together with one file per segment produced.

gpac -i source1 -i source2 -o res/live.m3u8:dual:profile=onDemand

This will generate live.m3u8 and live.mpd together with a single file per quality. Since the DASH profile is onDemand, the ISOBMFF file of each quality will also contain a segment index (not used in HLS).

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