mirror of
https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-09-20 19:10:18 +00:00
acb98b0938
We got the constants for G_LITTLE_ENDIAN and G_BIG_ENDIAN the wrong way around in some docs (fixes: #572392). Also mention G_BYTE_ORDER in the audio types section.
634 lines
20 KiB
Text
634 lines
20 KiB
Text
MIME types in GStreamer
|
|
|
|
What is a MIME type ?
|
|
=====================
|
|
|
|
A MIME type is a combination of two (short) strings (words)---the content type
|
|
and the content subtype. Content types are broad categories used for describing
|
|
almost all types of files: video, audio, text, and application are common
|
|
content types. The subtype further breaks the content type down into a more
|
|
specific type description, for example 'application/ogg', 'audio/raw',
|
|
'video/mpeg', or 'text/plain'.
|
|
|
|
So the content type and subtype make up a pair that describes the type of
|
|
information contained in a file. In multimedia processing, MIME types are used
|
|
to describe the type of information carried by a media stream. In GStreamer, we
|
|
use MIME types in the same way, to identify the types of information that are
|
|
allowed to pass between GStreamer elements. The MIME type is part of a GstCaps
|
|
object that describes a media stream. Besides a MIME type, a GstCaps object also
|
|
contains a name and some stream properties (GstProps, which hold combinations of
|
|
key/value pairs).
|
|
|
|
An example of a MIME type is 'video/mpeg'. A corresponding GstCaps could be
|
|
created using code:
|
|
|
|
GstCaps *caps = gst_caps_new_simple ("video/mpeg",
|
|
"width", G_TYPE_INT, 384,
|
|
"height", G_TYPE_INT, 288,
|
|
NULL);
|
|
|
|
MIME types and their corresponding properties are of major importance in
|
|
GStreamer for uniquely identifying media streams. Therefore, we define them
|
|
per media type. All GStreamer plugins should keep to this definition.
|
|
|
|
Official MIME media types are assigned by the IANA. Current assignments are at
|
|
http://www.iana.org/assignments/media-types/.
|
|
|
|
The problems
|
|
============
|
|
|
|
Some streams may have MIME types or GstCaps that do not fully describe the
|
|
stream. In most cases, this is not a problem, though. For example, if a stream
|
|
contains Ogg/Vorbis data (which is of type 'application/ogg'), we don't need to
|
|
know the samplerate of the raw audio stream, since we can't play the encoded
|
|
audio anyway. The samplerate is, however, important for raw audio, so a decoder
|
|
would need to retrieve the samplerate from the Ogg/Vorbis stream headers (the
|
|
headers are part of the bytestream) in order to pass it on in the GstCaps that
|
|
belongs to the decoded audio (which becomes a type like 'audio/raw'). However,
|
|
other plugins might want to know such properties, even for compressed streams.
|
|
One such example is an AVI muxer, which does want to know the samplerate of an
|
|
audio stream, even when it is compressed.
|
|
|
|
Another problem is that many media types can be defined in multiple ways. For
|
|
example, MJPEG video can be defined as 'video/jpeg', 'video/mjpeg',
|
|
'image/jpeg', 'video/x-msvideo' with a compression of (fourcc) MJPG, etc.
|
|
None of these is really official, since there isn't an official mimetype
|
|
for encoded MJPEG video.
|
|
|
|
The main focus of this document is to propose a standardized set of MIME types
|
|
and properties that will be used by the GStreamer plugins.
|
|
|
|
Different types of streams
|
|
==========================
|
|
|
|
There are several types of media streams. The most important distinction will be
|
|
container formats, audio codecs and video codecs. Container formats are
|
|
bytestreams that contain one or more substreams inside it, and don't provide any
|
|
direct media data itself. Examples are Quicktime, AVI or MPEG System Stream.
|
|
They mostly contain of a set of headers that define the media streams that are
|
|
packed inside the container, along with the media data itself.
|
|
|
|
Video codecs and audio codecs describe encoded audio or video data. Examples are
|
|
MPEG-1 video, DivX video, MPEG-1 layer 3 (MP3) audio or Ogg/Vorbis audio.
|
|
Actually, Ogg is a container format too (for Vorbis audio), but these are
|
|
usually used in conjunction with each other.
|
|
|
|
Finally, there are the somewhat obvious (but not commonly encountered as files)
|
|
raw data formats.
|
|
|
|
Container formats
|
|
-----------------
|
|
|
|
1 - AVI (Microsoft RIFF/AVI)
|
|
MIME type: video/x-msvideo
|
|
Properties:
|
|
Parser: avidemux, ffdemux_avi
|
|
Formatter: avimux
|
|
|
|
2 - Quicktime (Apple)
|
|
MIME type: video/quicktime
|
|
Properties:
|
|
Parser: qtdemux
|
|
Formatter:
|
|
|
|
3 - MPEG (MPEG LA)
|
|
MIME type: video/mpeg
|
|
Properties: 'systemstream' = TRUE (BOOLEAN)
|
|
Parser: mpegdemux, ffdemux_mpeg (PS), ffdemux_mpegts (TS), dvddemux
|
|
Formatter: mplex
|
|
|
|
4 - ASF (Microsoft)
|
|
MIME type: video/x-ms-asf
|
|
Properties:
|
|
Parser: asfdemux, ffdemux_asf
|
|
Formatter: asfmux
|
|
|
|
5 - WAV (Microsoft RIFF/WAV)
|
|
MIME type: audio/x-wav
|
|
Properties:
|
|
Parser: wavparse, ffdemux_wav
|
|
Formatter: wavenc
|
|
|
|
6 - RealMedia (Real)
|
|
MIME type: application/vnd.rn-realmedia
|
|
Properties: 'systemstream' = TRUE (BOOLEAN)
|
|
Parser: rmdemux, ffdemux_rm
|
|
Formatter:
|
|
|
|
7 - DV (Digital Video)
|
|
MIME type: video/x-dv
|
|
Properties: 'systemstream' = TRUE (BOOLEAN)
|
|
Parser: gst1394, ffdemux_dv
|
|
Formatter:
|
|
|
|
8 - Ogg (Xiph)
|
|
MIME type: application/ogg
|
|
Properties:
|
|
Parser: oggdemux
|
|
Formatter: oggmux
|
|
|
|
9 - Matroska
|
|
MIME type: video/x-mkv
|
|
Properties:
|
|
Parser: matroskademux, ffdemux_matroska
|
|
Formatter: matroskamux
|
|
|
|
10 - Shockwave (Macromedia)
|
|
MIME type: application/x-shockwave-flash
|
|
Properties:
|
|
Parser: swfdec, ffdemux_swf
|
|
Formatter:
|
|
|
|
11 - AU audio (Sun)
|
|
MIME type: audio/x-au
|
|
Properties:
|
|
Parser: auparse, ffdemux_au
|
|
Formatter:
|
|
|
|
12 - Mod audio
|
|
MIME type: audio/x-mod
|
|
Properties:
|
|
Parser: modplug, mikmod
|
|
Formatter:
|
|
|
|
13 - FLX video
|
|
MIME type: video/x-fli
|
|
Properties:
|
|
Parser: flxdec
|
|
Formatter:
|
|
|
|
14 - Monkeyaudio
|
|
MIME type: application/x-ape
|
|
Properties:
|
|
Parser:
|
|
Formatter:
|
|
|
|
15 - AIFF audio
|
|
MIME type: audio/x-aiff
|
|
Properties:
|
|
Parser:
|
|
Formatter:
|
|
|
|
16 - SID audio
|
|
MIME type: audio/x-sid
|
|
Properties:
|
|
Parser: siddec
|
|
Formatter:
|
|
|
|
Please note that we try to keep these MIME types as similar as possible to the
|
|
MIME types used as standards in Gnome (Gnome-VFS/Nautilus) and KDE
|
|
(Konqueror). Both will (in future) stick to a shared-mime-info database that
|
|
is hosted on freedesktop.org, and bases itself on IANA.
|
|
|
|
Also, there is a very thin line between audio codecs and audio containers
|
|
(take mp3 vs. sid, etc.). This is just a per-case thing right now and needs to
|
|
be documented further.
|
|
|
|
Video codecs
|
|
------------
|
|
|
|
For convenience, the fourcc codes used in the AVI container format will be
|
|
listed along with the MIME type and optional properties.
|
|
|
|
Optional properties for all video formats are the following:
|
|
|
|
width = 1 - MAXINT (INT)
|
|
height = 1 - MAXINT (INT)
|
|
pixel_width = 1 - MAXINT (INT, with pixel_height forms aspect ratio)
|
|
pixel_height = 1 - MAXINT (INT, with pixel_width forms aspect ratio)
|
|
framerate = 0 - MAXFLOAT (FLOAT)
|
|
|
|
1 - MPEG-1, -2 and -4 video (ISO/LA MPEG)
|
|
MIME type: video/mpeg
|
|
Properties: systemstream = FALSE (BOOLEAN)
|
|
mpegversion = 1/2/4 (INT)
|
|
Known fourccs: MPEG, MPGI
|
|
Encoder: mpeg1enc, mpeg2enc
|
|
Decoder: mpeg1dec, mpeg2dec, mpeg2subt
|
|
|
|
2 - DivX 3.x, 4.x and 5.x video (divx.com)
|
|
MIME type: video/x-divx
|
|
Properties:
|
|
Optional properties: divxversion = 3/4/5 (INT)
|
|
Known fourccs: DIV3, DIV4, DIV5, DIVX, DX50, DIVX, divx
|
|
Encoder: divxenc
|
|
Decoder: divxdec, ffdec_mpeg4
|
|
|
|
3 - Microsoft MPEG 4.1, 4.2 and 4.3
|
|
MIME type: video/x-msmpeg
|
|
Properties:
|
|
Optional properties: msmpegversion = 41/42/43 (INT)
|
|
Known fourccs: MPG4, MP42, MP43
|
|
Encoder: ffenc_msmpeg4, ffenc_msmpeg4v1, ffenc_msmpeg4v2
|
|
Decoder: ffdec_msmpeg4, ffdec_msmpeg4v1, ffdec_msmpeg4v2
|
|
|
|
4 - Motion-JPEG (official and extended)
|
|
MIME type: video/x-jpeg
|
|
Properties:
|
|
Known fourccs: MJPG (YUY2 MJPEG), JPEG (any), PIXL (Pinnacle/Miro), VIXL
|
|
Encoder: jpegenc
|
|
Decoder: jpegdec, ffdec_mjpeg
|
|
|
|
5 - Sorensen (Quicktime - SVQ1/SVQ3)
|
|
MIME types: video/x-svq
|
|
Properties: svqversion = 1/3 (INT)
|
|
Encoder:
|
|
Decoder: ffdec_svq1, ffdec_svq3
|
|
|
|
6 - H263 and related codecs
|
|
MIME type: video/x-h263
|
|
Properties:
|
|
Known fourccs: H263/h263, i263, L263, M263/m263, s263, x263, VDOW, VIVO
|
|
Encoder: ffenc_h263, ffenc_h263p
|
|
Decoder: ffdec_h263, ffdec_h263i
|
|
|
|
7 - RealVideo (Real)
|
|
MIME type: video/x-pn-realvideo
|
|
Properties: rmversion = "1"/"2"/"3"/"4" (INT)
|
|
Known fourccs: RV10, RV20, RV30, RV40
|
|
Encoder: ffenc_rv10
|
|
Decoder: ffdec_rv10, ffdec_rv20
|
|
|
|
8 - Digital Video (DV)
|
|
MIME type: video/x-dv
|
|
Properties: systemstream = FALSE (BOOLEAN)
|
|
Known fourccs: DVSD/dvsd (SDTV), dvhd (HDTV), dvsl (SDTV LongPlay)
|
|
Encoder: ffenc_dvvideo
|
|
Decoder: dvdec, ffdec_dvvideo
|
|
|
|
9 - Windows Media Video 1, 2 and 3 (WMV)
|
|
MIME type: video/x-wmv
|
|
Properties: wmvversion = 1/2/3 (INT)
|
|
Encoder: ffenc_wmv1, ffenc_wmv2, none
|
|
Decoder: ffdec_wmv1, ffdec_wmv2, none
|
|
|
|
10 - XviD (xvid.org)
|
|
MIME type: video/x-xvid
|
|
Properties:
|
|
Known fourccs: xvid, XVID
|
|
Encoder: xvidenc
|
|
Decoder: xviddec, ffdec_mpeg4
|
|
|
|
11 - 3IVX (3ivx.org)
|
|
MIME type: video/x-3ivx
|
|
Properties:
|
|
Known fourccs: 3IV0, 3IV1, 3IV2
|
|
Encoder:
|
|
Decoder:
|
|
|
|
12 - Ogg/Tarkin (Xiph)
|
|
MIME type: video/x-tarkin
|
|
Properties:
|
|
Encoder:
|
|
Decoder:
|
|
|
|
13 - VP3
|
|
MIME type: video/x-vp3
|
|
Properties:
|
|
Encoder:
|
|
Decoder: ffdec_vp3
|
|
|
|
14 - Ogg/Theora (Xiph, VP3-like)
|
|
MIME type: video/x-theora
|
|
Properties:
|
|
Encoder: theoraenc
|
|
Decoder: theoradec, ffdec_theora
|
|
This is the raw stream that comes out of an ogg file.
|
|
|
|
15 - Huffyuv
|
|
MIME type: video/x-huffyuv
|
|
Properties:
|
|
Known fourccs: HFYU
|
|
Encoder:
|
|
Decoder: ffdec_hfyu
|
|
|
|
16 - FF Video 1 (FFMPEG)
|
|
MIME type: video/x-ffv
|
|
Properties: ffvversion = 1 (INT)
|
|
Encoder:
|
|
Decoder: ffdec_ffv1
|
|
|
|
17 - H264
|
|
MIME type: video/x-h264
|
|
Properties:
|
|
Known fourccs: VSSH
|
|
Encoder:
|
|
Decoder: ffdec_h264
|
|
|
|
18 - Indeo 3 (Intel)
|
|
MIME type: video/x-indeo
|
|
Properties: indeoversion = 3 (INT)
|
|
Encoder:
|
|
Decoder: ffdec_indeo3
|
|
|
|
19 - Portable Network Graphics (PNG)
|
|
MIME type: video/x-png
|
|
Properties:
|
|
Encoder: pngenc
|
|
Decoder: pngdec, gdkpixbufdec
|
|
|
|
20 - Cinepak
|
|
MIME type: video/x-cinepak
|
|
Properties:
|
|
Encoder:
|
|
Decoder: ffdec_cinepak
|
|
|
|
TODO: subsampling information for YUV?
|
|
|
|
TODO: colorspace identifications for MJPEG? How?
|
|
|
|
TODO: how to distinguish MJPEG-A/B (Quicktime) and lossless JPEG?
|
|
|
|
TODO: divx4/divx5/xvid/3ivx/mpeg-4 - how to make them overlap? (all
|
|
ISO MPEG-4 compatible)
|
|
|
|
3c) Audio Codecs
|
|
----------------
|
|
For convenience, the two-byte hexcodes (as used for identification in AVI files)
|
|
are also given.
|
|
|
|
Properties for all audio formats include the following:
|
|
|
|
rate = 1 - MAXINT (INT, sampling rate)
|
|
channels = 1 - MAXINT (INT, number of audio channels)
|
|
|
|
1 - Alaw Raw Audio
|
|
MIME type: audio/x-alaw
|
|
Properties:
|
|
Encoder: alawenc
|
|
Decoder: alawdec
|
|
|
|
2 - Mulaw Raw Audio
|
|
MIME type: audio/x-mulaw
|
|
Properties:
|
|
Encoder: mulawenc
|
|
Decoder: mulawdec
|
|
|
|
3 - MPEG-1 layer 1/2/3 audio
|
|
MIME type: audio/mpeg
|
|
Properties: mpegversion = 1 (INT)
|
|
layer = 1/2/3 (INT)
|
|
Encoder: lame, ffdec_mp3
|
|
Decoder: mad
|
|
|
|
4 - Ogg/Vorbis
|
|
MIME type: audio/x-vorbis
|
|
Encoder: rawvorbisenc (vorbisenc does rawvorbisenc+oggmux)
|
|
Decoder: vorbisdec
|
|
|
|
5 - Windows Media Audio 1, 2 and 3 (WMA)
|
|
MIME type: audio/x-wma
|
|
Properties: wmaversion = 1/2/3 (INT)
|
|
Encoder:
|
|
Decoder: ffdec_wmav1, ffdec_wmav2, none
|
|
|
|
6 - AC3
|
|
MIME type: audio/x-ac3
|
|
Properties:
|
|
Encoder: ffenc_ac3
|
|
Decoder: a52dec, ac3parse
|
|
|
|
7 - FLAC (Free Lossless Audio Codec)
|
|
MIME type: audio/x-flac
|
|
Properties:
|
|
Encoder: flacenc
|
|
Decoder: flacdec, ffdec_flac
|
|
|
|
8 - MACE 3/6 (Quicktime audio)
|
|
MIME type: audio/x-mace
|
|
Properties: maceversion = 3/6 (INT)
|
|
Encoder:
|
|
Decoder: ffdec_mace3, ffdec_mace6
|
|
|
|
9 - MPEG-4 AAC
|
|
MIME type: audio/mpeg
|
|
Properties: mpegversion = 4 (INT)
|
|
Encoder: faac
|
|
Decoder: faad
|
|
|
|
10 - (IMA) ADPCM (Quicktime/WAV/Microsoft/4XM)
|
|
MIME type: audio/x-adpcm
|
|
Properties: layout = "quicktime"/"wav"/"microsoft"/"4xm"/"g721"/"g722"/"g723_3"/"g723_5" (STRING)
|
|
Encoder: ffenc_adpcm_ima_[qt/wav/dk3/dk4/ws/smjpeg], ffenc_adpcm_[ms/4xm/xa/adx/ea]
|
|
Decoder: ffdec_adpcm_ima_[qt/wav/dk3/dk4/ws/smjpeg], ffdec_adpcm_[ms/4xm/xa/adx/ea]
|
|
|
|
Note: The difference between each of these four PCM formats is the number
|
|
of samples packed together per channel. For WAV, for example, each
|
|
sample is 4 bit, and 8 samples are packed together per channel in the
|
|
bytestream. For the others, refer to technical documentation. We
|
|
probably want to distinguish these differently, but I don't know how,
|
|
yet.
|
|
|
|
11 - RealAudio (Real)
|
|
MIME type: audio/x-pn-realaudio
|
|
Properties: raversion ="1"/"2" (INT)
|
|
Known fourccs: 14_4, 28_8
|
|
Encoder:
|
|
Decoder: ffdec_real_144 / ffdec_real_288
|
|
|
|
12 - DV Audio
|
|
MIME type: audio/x-dv
|
|
Properties:
|
|
Encoder:
|
|
Decoder:
|
|
|
|
13 - GSM Audio
|
|
MIME type: audio/x-gsm
|
|
Properties:
|
|
Encoder: gsmenc, rtpgsmenc
|
|
Decoder: gsmdec, rtpgsmparse
|
|
|
|
14 - Speex audio
|
|
MIME type: audio/x-speex
|
|
Properties:
|
|
Encoder: speexenc
|
|
Decoder: speexdec
|
|
|
|
15 - QDM2
|
|
MIME type: audio/x-qdm2
|
|
Properties:
|
|
|
|
16 - Sony ATRAC4 (detected inside realmedia and wave/avi streams, nothing to decode it yet)
|
|
MIME type: audio/x-vnd.sony.atrac3
|
|
Properties:
|
|
Encoder:
|
|
Decoder:
|
|
|
|
17 - Ensoniq PARIS audio
|
|
MIME type: audio/x-paris
|
|
Properties:
|
|
Encoder:
|
|
Decoder:
|
|
|
|
18 - Amiga IFF / SVX8 / SV16 audio
|
|
MIME type: audio/x-svx
|
|
Properties:
|
|
Encoder:
|
|
Decoder:
|
|
|
|
19 - Sphere NIST audio
|
|
MIME type: audio/x-nist
|
|
Properties:
|
|
Encoder:
|
|
Decoder:
|
|
|
|
20 - Sound Blaster VOC audio
|
|
MIME type: audio/x-voc
|
|
Properties:
|
|
Encoder:
|
|
Decoder:
|
|
|
|
21 - Berkeley/IRCAM/CARL audio
|
|
MIME type: audio/x-ircam
|
|
Properties:
|
|
Encoder:
|
|
Decoder:
|
|
|
|
22 - Sonic Foundry's 64 bit RIFF/WAV
|
|
MIME type: audio/x-w64
|
|
Properties:
|
|
Encoder:
|
|
Decoder:
|
|
|
|
TODO: adpcm/dv needs confirmation from someone with knowledge...
|
|
|
|
Raw formats
|
|
-----------
|
|
|
|
Raw formats contain unencoded, raw media information. These are rather rare from
|
|
an end user point of view since raw media files have historically been
|
|
prohibitively large ... hence the multitude of encoding formats.
|
|
|
|
Raw video formats require the following common properties, in addition to
|
|
format-specific properties:
|
|
|
|
width = 1 - MAXINT (INT)
|
|
height = 1 - MAXINT (INT)
|
|
|
|
1 - Raw Video (YUV/YCbCr)
|
|
MIME type: video/x-raw-yuv
|
|
Properties: 'format' = 'XXXX' (fourcc)
|
|
Known fourccs: YUY2, I420, Y41P, YVYU, UYVY, etc.
|
|
Properties:
|
|
|
|
Some raw video formats have implicit alignment rules. We should discuss this
|
|
more. Also, some formats have multiple fourccs (e.g. IYUV/I420 or
|
|
YUY2/YUYV). For each of these, we only use one (e.g. I420 and YUY2).
|
|
|
|
Currently recognized formats:
|
|
|
|
YUY2: packed, Y-U-Y-V order, U/V hor 2x subsampled (YUV-4:2:2, 16 bpp)
|
|
YVYU: packed, Y-V-Y-U order, U/V hor 2x subsampled (YUV-4:2:2, 16 bpp)
|
|
UYVY: packed, U-Y-V-Y order, U/V hor 2x subsampled (YUV-4:2:2, 16 bpp)
|
|
Y41P: packed, UYVYUYVYYYYY order, U/V hor 4x subsampled (YUV-4:1:1, 12 bpp)
|
|
IUY2: packed, U-Y-V order, not subsampled (YUV-1:1:1, 24 bpp)
|
|
|
|
Y42B: planar, Y-U-V order, U/V hor 2x subsampled (YUV-4:2:2, 16 bpp)
|
|
YV12: planar, Y-V-U order, U/V hor+ver 2x subsampled (YUV-4:2:0, 12 bpp)
|
|
I420: planar, Y-U-V order, U/V hor+ver 2x subsampled (YUV-4:2:0, 12 bpp)
|
|
Y41B: planar, Y-U-V order, U/V hor 4x subsampled (YUV-4:1:1, 12bpp)
|
|
YUV9: planar, Y-U-V order, U/V hor+ver 4x subsampled (YUV-4:1:0, 9bpp)
|
|
YVU9: planar, Y-V-U order, U/V hor+ver 4x subsampled (YUV-4:1:0, 9bpp)
|
|
|
|
Y800: one-plane (Y-only, YUV-4:0:0, 8bpp)
|
|
|
|
See http://www.fourcc.org/ for more information.
|
|
|
|
Note: YUV-4:4:4 (both planar and packed, in multiple orders) are missing.
|
|
|
|
2 - Raw video (RGB)
|
|
MIME type: video/x-raw-rgb
|
|
Properties: endianness = 1234/4321 (INT) <- use G_LITTLE_ENDIAN/G_BIG_ENDIAN
|
|
depth = 15/16/24 (INT, color depth)
|
|
bpp = 16/24/32 (INT, bits used to store each pixel)
|
|
red_mask = bitmask (0x..) (INT)
|
|
green_mask = bitmask (0x..) (INT)
|
|
blue_mask = bitmask (0x..) (INT)
|
|
|
|
24 and 32 bit RGB should always be specified as big endian, since any little
|
|
endian format can be transformed into big endian by rearranging the color
|
|
masks. 15 and 16 bit formats should generally have the same byte order as
|
|
the CPU.
|
|
|
|
Color masks are interpreted by loading 'bpp' number of bits using the given
|
|
'endianness', and masking and shifting by each color mask. Loading a 24-bit
|
|
value cannot be done directly, but one can perform an equivalent operation.
|
|
|
|
Examples:
|
|
msb .. lsb
|
|
- memory: RRRRRRRR GGGGGGGG BBBBBBBB RRRRRRRR GGGGGGGG ...
|
|
bpp = 24
|
|
depth = 24
|
|
endianness = 4321 (G_BIG_ENDIAN)
|
|
red_mask = 0xff0000
|
|
green_mask = 0x00ff00
|
|
blue_mask = 0x0000ff
|
|
|
|
- memory: xRRRRRGG GGGBBBBB xRRRRRGG GGGBBBBB xRRRRRGG ...
|
|
bpp = 16
|
|
depth = 15
|
|
endianness = 4321 (G_BIG_ENDIAN)
|
|
red_mask = 0x7c00
|
|
green_mask = 0x03e0
|
|
blue_mask = 0x003f
|
|
|
|
- memory: GGGBBBBB xRRRRRGG GGGBBBBB xRRRRRGG GGGBBBBB ...
|
|
bpp = 16
|
|
depth = 15
|
|
endianness = 1234 (G_LITTLE_ENDIAN)
|
|
red_mask = 0x7c00
|
|
green_mask = 0x03e0
|
|
blue_mask = 0x003f
|
|
|
|
The raw audio formats require the following common properties, in addition to
|
|
format-specific properties:
|
|
|
|
rate = 1 - MAXINT (INT, sampling rate)
|
|
channels = 1 - MAXINT (INT, number of audio channels)
|
|
endianness = 1234/4321 (INT) <- use G_LITTLE_ENDIAN/G_BIG_ENDIAN/G_BYTE_ORDER
|
|
|
|
3 - Raw audio (integer format)
|
|
MIME type: audio/x-raw-int
|
|
properties: width = 8/16/24/32 (INT, bits used to store each sample)
|
|
depth = 8 - 32 (INT, bits actually used per sample)
|
|
signed = TRUE/FALSE (BOOLEAN)
|
|
|
|
4 - Raw audio (floating point format)
|
|
MIME type: audio/x-raw-float
|
|
Properties: width = 32/64 (INT)
|
|
buffer-frames: number of audio frames per buffer, 0=undefined
|
|
|
|
Plugin Guidelines
|
|
=================
|
|
|
|
So, a short bit on what plugins should do. Above, I've stated that audio
|
|
properties like 'channels' and 'rate' or video properties like 'width' and
|
|
'height' are all optional. This doesn't mean you can just simply omit them and
|
|
everything will still work!
|
|
|
|
An example is the best way to explain all this. AVI needs the width, height,
|
|
rate and channels for the AVI header. So if these properties are missing, the
|
|
avimux element cannot properly create the AVI header. On the other hand, MPEG
|
|
doesn't have such properties in its header, so the mpegdemux element would need
|
|
to parse the separate streams in order to find them out. We don't want that
|
|
either, because a plugin only does one job. So normally, mpegdemux and avimux
|
|
wouldn't allow transcoding. To solve this problem, there are stream parser
|
|
elements (such as mpegaudioparse, ac3parse and mpeg1videoparse).
|
|
|
|
Conclusions to draw from here: a plugin gives info it can provide as seen from
|
|
its own task/job. If it can't, other elements might still need it and a stream
|
|
parser needs to be written if it doesn't already exist.
|
|
|
|
On properties that can be described by one of these (properties such as 'width',
|
|
'height', 'fps', etc.): they're forbidden and should be handled using filtered
|
|
caps.
|
|
|
|
Status of this document
|
|
=======================
|
|
|
|
Not all plugins strictly follow these guidelines yet, but these are the official
|
|
types. Plugins not following these specs either use extensions that should be
|
|
documented, or are buggy (and should be fixed).
|
|
|
|
Blame Ronald Bultje <rbultje@ronald.bitfreak.net> aka BBB for any mistakes in
|
|
this document.
|