GStreamer pwg: ch. 16

 

16.     Media Types and Properties

 

Ÿ   가능하면 존재하는 type을 사용

Ÿ   type 생성 시 GStreamer developer와 IRC mailing list를 통해 discuss

Ÿ   새로운 format의 name이 conflict를 발생하는지 확인

Ÿ   명확한 name 사용

    n  ex. mp3에 대해서 audio/compressed가 아닌 audio/mp3를 사용

Ÿ   Defined Types의 list에 명확하게 추가

 

 

16.1.     building a simple format for testing

 

media type과 property에 대한 naming guideline

media type은 IANA에 의해 정의된 Mime-type과 동일해야 함

혹은 "type/x-name" 이어야 함 (type은 audio, video 등)

 

 

16.2.     Typefind functions and Autoplugging

 

Ÿ   typefinding

    n  data stream의 type을 찾는 과정

    n  구성

        s   typefind functions

            -       개수 제한 없음

            -       input stream에서 하나 이상의 type을 인식하는 함수

        s   typefind function들을 등록하는 함수

            -       Typefind Core

    n  Typefind core 상에서 autoplugger를 작성

        s   input streamdmfh 동적으로 type을 찾고 pipeline을 구성

 

typefind functions

보통 gst-plugins-base/gst/typefind/gsttypefindfunctions.c 여기에 위치

 

AVI file들을 인식하는 example

    Ÿ   "RIFF" tag로 시작 + file size + "AVI" tag

 

static GstStaticCaps avi_caps = GST_STATIC_CAPS ("video/x-msvideo"); #define AVI_CAPS gst_static_caps_get(&avi_caps)   static void gst_avi_typefind_function (GstTypeFind *tf,               gpointer     pointer) {   guint8 *data = gst_type_find_peek (tf, 0, 12);     if (data &&       GUINT32_FROM_LE (&((guint32 *) data)[0]) == GST_MAKE_FOURCC ('R','I','F','F') &&       GUINT32_FROM_LE (&((guint32 *) data)[2]) == GST_MAKE_FOURCC ('A','V','I',' ')) {     gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, AVI_CAPS);   } }   GST_TYPE_FIND_REGISTER_DEFINE(avi, "video/x-msvideo", GST_RANK_PRIMARY,     gst_avi_typefind_function, "avi", AVI_CAPS, NULL, NULL);   static gboolean plugin_init (GstPlugin *plugin) {   return GST_TYPEFIND_REGISTER(avi, plugin); }

 

 

16.3.     List of Defined Types

 

types

    Ÿ   audio, video, container, subtitle, etc.

    Ÿ   type의 정의는 IANA의 rule을 따르도록 했음

        n  http://www.iana.org/assignments/media-types

 

대부분의 property들은 container header에서 추출될 수 있음

없는 경우 stream header를 parsing 하여 추출

 

Ÿ   AVI haeder

    n  sample rate등을 제공

    n  MPEG system은 제공하지 않음

    n  즉, AVI stream demuxcer는 samplerate를 property로 MPEG audio system을 위해 제공해야 함

    n  이런 data를 필요로 하는 decoder는 stream parsr에게 두가지의 추출을 요청해야함

        s   header의 추출

        s   stream으로부터의 계산

 

audio types

Media Type	Description
All audio types.
audio/*	All audio types
channels	integer
channel-mask	bitmask
format	string
layout	string
All raw audio types.
audio/x-raw	Unstructured and uncompressed raw audio data.
All encoded audio types.
audio/x-ac3	AC-3 or A52 audio streams.
audio/x-adpcm	ADPCM Audio streams.
block_align	integer
audio/x-cinepak	Audio as provided in a Cinepak (Quicktime) stream.
audio/x-dv	Audio as provided in a Digital Video stream.
audio/x-flac	Free Lossless Audio codec (FLAC).
audio/x-gsm	Data encoded by the GSM codec.
audio/x-alaw	A-Law Audio.
audio/x-mulaw	Mu-Law Audio.
audio/x-mace	MACE Audio (used in Quicktime).
audio/mpeg	Audio data compressed using the MPEG audio encoding scheme.
framed	boolean
layer	integer
bitrate	integer
audio/x-qdm2	Data encoded by the QDM version 2 codec.
audio/x-pn-realaudio	Realmedia Audio data.
audio/x-speex	Data encoded by the Speex audio codec
audio/x-vorbis	Vorbis audio data
audio/x-wma	Windows Media Audio
audio/x-paris	Ensoniq PARIS audio
audio/x-svx	Amiga IFF / SVX8 / SV16 audio
audio/x-nist	Sphere NIST audio
audio/x-voc	Sound Blaster VOC audio
audio/x-ircam	Berkeley/IRCAM/CARL audio
audio/x-w64	Sonic Foundry's 64 bit RIFF/WAV

 

video types

Media Type	Description
All video types.
video/*	All video types
height	integer
framerate	fraction
max-framerate	fraction
views	integer
interlace-mode	string
chroma-site	string
colorimetry	string
pixel-aspect-ratio	fraction
format	string
All raw video types.
video/x-raw	Unstructured and uncompressed raw video data.
All encoded video types.
video/x-3ivx	3ivx video.
video/x-divx	DivX video.
video/x-dv	Digital Video.
video/x-ffv	FFMpeg video.
video/x-h263	H-263 video.
h263version	string
video/x-h264	H-264 video.
video/x-huffyuv	Huffyuv video.
video/x-indeo	Indeo video.
video/x-intel-h263	H-263 video.
video/x-jpeg	Motion-JPEG video.
video/mpeg	MPEG video.
systemstream	boolean
video/x-msmpeg	Microsoft MPEG-4 video deviations.
video/x-msvideocodec	Microsoft Video 1 (oldish codec).
video/x-pn-realvideo	Realmedia video.
video/x-rle	RLE animation format.
depth	integer
palette_data	GstBuffer
video/x-svq	Sorensen Video.
video/x-tarkin	Tarkin video.
video/x-theora	Theora video.
video/x-vp3	VP-3 video.
video/x-wmv	Windows Media Video
video/x-xvid	XviD video.
All image types.
image/gif	Graphics Interchange Format.
image/jpeg	Joint Picture Expert Group Image.
image/png	Portable Network Graphics Image.
image/tiff	Tagged Image File Format.

 

container types

Media Type	Description
video/x-ms-asf	Advanced Streaming Format (ASF).
video/x-msvideo	AVI.
video/x-dv	Digital Video.
video/x-matroska	Matroska.
video/mpeg	Motion Pictures Expert Group System Stream.
application/ogg	Ogg.
video/quicktime	Quicktime.
application/vnd.rn-realmedia	RealMedia.
audio/x-wav	WAV.