# Types and Properties

There is a very large set of possible types that may be used to pass data between elements. Indeed, each new element that is defined may use a new data format (though unless at least one other element recognises that format, it will be most likely be useless since nothing will be able to link with it).

In order for types to be useful, and for systems like autopluggers to work, it is neccessary that all elements agree on the type definitions, and which properties are required for each type. The &GStreamer; framework itself simply provides the ability to define types and parameters, but does not fix the meaning of types and parameters, and does not enforce standards on the creation of new types. This is a matter for a policy to decide, not technical systems to enforce.

For now, the policy is simple:

- Do not create a new type if you could use one which already exists.

- If creating a new type, discuss it first with the other &GStreamer; developers, on at least one of: IRC, mailing lists, the &GStreamer; wiki.

- Try to ensure that the name for a new format is as unlikely to conflict with anything else created already, and is not a more generalised name than it should be. For example: "audio/compressed" would be too generalised a name to represent audio data compressed with an mp3 codec. Instead "audio/mp3" might be an appropriate name, or "audio/compressed" could exist and have a property indicating the type of compression used.

- Ensure that, when you do create a new type, you specify it clearly, and get it added to the list of known types so that other developers can use the type correctly when writing their elements.

## Building a Simple Format for Testing

If you need a new format that has not yet been defined in our , you will want to have some general guidelines on mimetype naming, properties and such. A mimetype would ideally be one defined by IANA; else, it should be in the form type/x-name, where type is the sort of data this mimetype handles (audio, video, ...) and name should be something specific for this specific type. Audio and video mimetypes should try to support the general audio/video properties (see the list), and can use their own properties, too. To get an idea of what properties we think are useful, see (again) the list.

Take your time to find the right set of properties for your type. There is no reason to hurry. Also, experimenting with this is generally a good idea. Experience learns that theoretically thought-out types are good, but they still need practical use to assure that they serve their needs. Make sure that your property names do not clash with similar properties used in other types. If they match, make sure they mean the same thing; properties with different types but the same names are not allowed.

## Typefind Functions and Autoplugging

WRITEME

## List of Defined Types

Below is a list of all the defined types in &GStreamer;. They are split up in separate tables for audio, video, container, subtitle and other types, for the sake of readability. Below each table might follow a list of notes that apply to that table. In the definition of each type, we try to follow the types and rules as defined by IANA for as far as possible.

Jump directly to a specific table:

Note that many of the properties are not required, but rather optional properties. This means that most of these properties can be extracted from the container header, but that - in case the container header does not provide these - they can also be extracted by parsing the stream header or the stream content. The policy is that your element should provide the data that it knows about by only parsing its own content, not another element's content. Example: the AVI header provides samplerate of the contained audio stream in the header. MPEG system streams don't. This means that an AVI stream demuxer would provide samplerate as a property for MPEG audio streams, whereas an MPEG demuxer would not. A decoder needing this data would require a stream parser in between two extract this from the header or calculate it from the stream.

### Table of Audio Types

Mime Type | Description | Property | Property Type | Property Values | Property Description
--- | --- | --- | --- | --- | ---
All audio types.
audio/* | All audio types | rate | integer | greater than 0 | The sample rate of the data, in samples (per channel) per second.
channels | integer | greater than 0 | The number of channels of audio data.
All raw audio types.
audio/x-raw-int | Unstructured and uncompressed raw fixed-integer audio data. | endianness | integer | G_BIG_ENDIAN (1234) or G_LITTLE_ENDIAN (4321) | The order of bytes in a sample. The value G_LITTLE_ENDIAN (4321) means little-endian (byte-order is least significant byte first). The value G_BIG_ENDIAN (1234) means big-endian (byte order is most significant byte first).
signed | boolean | TRUE or FALSE | Whether the values of the integer samples are signed or not. Signed samples use one bit to indicate sign (negative or positive) of the value. Unsigned samples are always positive.
width | integer | greater than 0 | Number of bits allocated per sample.
depth | integer | greater than 0 | The number of bits used per sample. This must be less than or equal to the width: If the depth is less than the width, the low bits are assumed to be the ones used. For example, a width of 32 and a depth of 24 means that each sample is stored in a 32 bit word, but only the low 24 bits are actually used.
audio/x-raw-float | Unstructured and uncompressed raw floating-point audio data. | endianness | integer | G_BIG_ENDIAN (1234) or G_LITTLE_ENDIAN (4321) | The order of bytes in a sample. The value G_LITTLE_ENDIAN (4321) means little-endian (byte-order is least significant byte first). The value G_BIG_ENDIAN (1234) means big-endian (byte order is most significant byte first).
width | integer | greater than 0 | The amount of bits used and allocated per sample.

buffer-frames

integer

greater than 0

The number of frames per buffer. The reason for this property is that the element does not need to reuse buffers or use data spanned over multiple buffers, so this property - when used rightly - will decrease latency. Note that some people think that this property is very ugly, whereas others think it is vital for the use of &GStreamer; in professional audio applications.

All encoded audio types.
audio/x-ac3 | AC-3 or A52 audio streams. |  |  |  | There are currently no specific properties defined or needed for this type.

audio/x-adpcm

ADPCM Audio streams.

layout

string

quicktime, wav, microsoft or 4xm.

The layout defines the packing of the samples in the stream. In ADPCM, most formats store multiple samples per channel together. This number of samples differs per format, hence the different layouts. On the long term, we probably want this variable to die and use something more descriptive, but this will do for now.

audio/x-dv | Audio as provided in a Digital Video stream. |  |  |  | There are currently no specific properties defined or needed for this type.
audio/x-flac | Free Lossless Audio codec (FLAC). |  |  |  | There are currently no specific properties defined or needed for this type.
audio/x-gsm | Data encoded by the GSM codec. |  |  |  | There are currently no specific properties defined or needed for this type.
audio/x-alaw | A-Law Audio. |  |  |  | There are currently no specific properties defined or needed for this type.
audio/x-mulaw | Mu-Law Audio. |  |  |  | There are currently no specific properties defined or needed for this type.
audio/x-mace | MACE Audio (used in Quicktime). | maceversion | integer | 3 or 6 | The version of the MACE audio codec used to encode the stream.
audio/mpeg | Audio data compressed using the MPEG audio encoding scehem. | mpegversion | integer | 1, 2 or 4 | The MPEG-version used for encoding the data. The value 1 refers to MPEG-1, -2 and -2.5 layer 1, 2 or 3. The values 2 and 4 refer to the MPEG-AAC audio encoding schemes.
framed | boolean | 0 or 1 | A true value indicates that each buffer contains exactly one frame. A false value indicates that frames and buffers do not necessarily match up.
layer | integer | 1, 2, or 3 | The compression scheme layer used to compress the data (only if mpegversion=1).
bitrate | integer | greater than 0 | The bitrate, in bits per second. For VBR (variable bitrate) MPEG data, this is the average bitrate.
audio/x-qdm2 | Data encoded by the QDM version 2 codec. |  |  |  | There are currently no specific properties defined or needed for this type.
audio/x-pn-realaudio | Realmedia Audio data. | raversion | integer | 1 or 2 | The version of the Real Audio codec used to encode the stream. 1 stands for a 14k4 stream, 2 stands for a 28k8 stream.
audio/x-speex | Data encoded by the Speex audio codec |  |  |  | There are currently no specific properties defined or needed for this type.
audio/x-vorbis | Vorbis audio data. |  |  |  | There are currently no specific properties defined or needed for this type.
audio/x-wma | Windows Media Audio | wmaversion | integer | 1 or 2 | The version of the WMA codec used to encode the stream.

### Table of Video Types

Mime Type | Description | Property | Property Type | Property Values | Property Description
--- | --- | --- | --- | --- | ---
All video types.
video/* | All video types | width | integer | greater than 0 | The width of the video image
height | integer | greater than 0 | The height of the video image
framerate | double | greater than 0 | The (average) framerate in frames per second. Note that this property does not guarantee in any way that it will actually come close to this value. If you need a fixed framerate, please use an element that provides that (such as videodrop).
All raw video types.

video/x-raw-yuv

YUV (or Y'Cb'Cr) video format.

format

fourcc

YUY2, YVYU, UYVY, Y41P, IYU2, Y42B, YV12, I420, Y41B, YUV9, YVU9, Y800

The layout of the video. See FourCC definition site for references and definitions. YUY2, YVYU and UYVY are 4:2:2 packed-pixel, Y41P is 4:1:1 packed-pixel and IYU2 is 4:4:4 packed-pixel. Y42B is 4:2:2 planar, YV12 and I420 are 4:2:0 planar, Y41B is 4:1:1 planar and YUV9 and YVU9 are 4:1:0 planar. Y800 contains Y-samples only (black/white).

video/x-raw-rgb | Red-Green-Blue (RBG) video. | bpp | integer | greater than 0 | The number of bits allocated per pixel. This is usually 16, 24 or 32.
depth | integer | greater than 0 | The number of bits used per pixel by the R/G/B components. This is usually 15, 16 or 24.
endianness | integer | G_BIG_ENDIAN (1234) or G_LITTLE_ENDIAN (4321) | The order of bytes in a sample. The value G_LITTLE_ENDIAN (4321) means little-endian (byte-order is least significant byte first). The value G_BIG_ENDIAN (1234) means big-endian (byte order is most significant byte first). For 24/32bpp, this should always be big endian because the byte order can be given in both.
red_mask, green_mask and blue_mask | integer | any | The masks that cover all the bits used by each of the samples. The mask should be given in the endianness specified above. This means that for 24/32bpp, the masks might be opposite to host byte order (if you are working on little-endian computers).
All encoded video types.
video/x-3ivx | 3ivx video. |  |  |  | There are currently no specific properties defined or needed for this type.
video/x-divx | DivX video. | divxversion | integer | 3, 4 or 5 | Version of the DivX codec used to encode the stream.
video/x-dx | Digital Video. | systemstream | boolean | FALSE | Indicates that this stream is not a system container stream.
video/x-ffv | FFMpeg video. | ffvversion | integer | 1 | Version of the FFMpeg video codec used to encode the stream.
video/x-h263 | H-263 video. |  |  |  | There are currently no specific properties defined or needed for this type.
video/x-h264 | H-264 video. |  |  |  | There are currently no specific properties defined or needed for this type.
video/x-huffyuv | Huffyuv video. |  |  |  | There are currently no specific properties defined or needed for this type.
video/x-indeo | Indeo video. | indeoversion | integer | 3 | Version of the Indeo codec used to encode this stream.
video/x-jpeg | Motion-JPEG video. |  |  |  | There are currently no specific properties defined or needed for this type. Note that video/x-jpeg only applies to Motion-JPEG pictures (YUY2 colourspace). RGB colourspace JPEG images are referred to as image/jpeg (JPEG image).
video/mpeg | MPEG video. | mpegversion | integer | 1, 2 or 4 | Version of the MPEG codec that this stream was encoded with. Note that we have different mimetypes for 3ivx, XviD, DivX and "standard" ISO MPEG-4. This is not a good thing and we're fully aware of this. However, we do not have a solution yet.
systemstream | boolean | FALSE | Indicates that this stream is not a system container stream.
video/x-msmpeg | Microsoft MPEG-4 video deviations. | msmpegversion | integer | 41, 42 or 43 | Version of the MS-MPEG-4-like codec that was used to encode this version. A value of 41 refers to MS MPEG 4.1, 42 to 4.2 and 43 to version 4.3.
video/x-pn-realvideo | Realmedia video. | rmversion | integer | 1, 2 or 3 | Version of the Real Video codec that this stream was encoded with.
video/x-svq | Sorensen Video. | svqversion | integer | 1 or 3 | Version of the Sorensen codec that the stream was encoded with.
video/x-tarkin | Tarkin video. |  |  |  | There are currently no specific properties defined or needed for this type.
video/x-theora | Theora video. |  |  |  | There are currently no specific properties defined or needed for this type.
video/x-vp3 | VP-3 video. |  |  |  | There are currently no specific properties defined or needed for this type. Note that we have different mimetypes for VP-3 and Theora, which is not necessarily a good idea. This could probably be improved.
video/x-wmv | Windows Media Video. | wmvversion | integer | 1 or 2 | Version of the WMV codec that the stream was encoded with.
video/x-xvid | XviD video. |  |  |  | There are currently no specific properties defined or needed for this type.
All image types.
image/jpeg | Joint Picture Expert Group Image. |  |  |  | There are currently no specific properties defined or needed for this type. Note that image/jpeg only applies to RGB-colourspace JPEG images; YUY2-colourspace JPEG pictures are referred to as video/x-jpeg ("Motion JPEG").
image/png | Portable Network Graphics Image. |  |  |  | There are currently no specific properties defined or needed for this type.

### Table of Container Types

Mime Type | Description | Property | Property Type | Property Values | Property Description
--- | --- | --- | --- | --- | ---
video/x-ms-asf | Advanced Streaming Format (ASF). |  |  |  | There are currently no specific properties defined or needed for this type.
video/x-msvideo | AVI. |  |  |  | There are currently no specific properties defined or needed for this type.
video/x-dv | Digital Video. | systemstream | boolean | TRUE | Indicates that this is a container system stream rather than an elementary video stream.
video/x-matroska | Matroska. |  |  |  | There are currently no specific properties defined or needed for this type.
video/mpeg | Motion Pictures Expert Group System Stream. | systemstream | boolean | TRUE | Indicates that this is a container system stream rather than an elementary video stream.
application/ogg | Ogg. |  |  |  | There are currently no specific properties defined or needed for this type.
video/quicktime | Quicktime. |  |  |  | There are currently no specific properties defined or needed for this type.
video/x-pn-realvideo | Digital Video. | systemstream | boolean | TRUE | Indicates that this is a container system stream rather than an elementary video stream.
audio/x-wav | WAV. |  |  |  | There are currently no specific properties defined or needed for this type.

### Table of Subtitle Types

Mime Type | Description | Property | Property Type | Property Values | Property Description
--- | --- | --- | --- | --- | ---
|  |  |  |  | None defined yet.

### Table of Other Types

Mime Type | Description | Property | Property Type | Property Values | Property Description
--- | --- | --- | --- | --- | ---
|  |  |  |  | None defined yet.