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gstreamer/gst/asfdemux
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Derek Lesho 8fe8ed3dd2 asfdemux: Always re-initialize metadata and global_metadata 
When transitioning from the PAUSED state, to the READY state, and back,
metadata and global_metadata are left uninitialized, unlike when the
demxuer transitions from NULL to READY, then to PAUSED.  I have found
this to cause a segmentation fault when fields in these structures are
set.
2020-04-08 11:06:27 +03:00
..
asfheaders.c asfdemux: add ASF_OBJ_METADATA_LIBRARY_OBJECT 2014-09-05 10:49:16 +03:00
asfheaders.h asfdemux: remove some unused cruft in internal headers 2019-05-25 14:19:54 +02:00
asfpacket.c asfdemux: Support reverse playback 2016-01-04 16:13:03 -05:00
asfpacket.h Fix FSF address 2012-11-03 20:40:37 +00:00
gstasf.c Fix FSF address 2012-11-03 20:40:37 +00:00
gstasfdemux.c asfdemux: Always re-initialize metadata and global_metadata 2020-04-08 11:06:27 +03:00
gstasfdemux.h docs: Port documentation to hotdoc 2019-05-13 17:00:00 -04:00
gstrtpasfdepay.c ugly: use new gst_element_class_add_static_pad_template() 2016-03-24 14:38:13 +02:00
gstrtpasfdepay.h Fix FSF address 2012-11-03 20:40:37 +00:00
gstrtspwms.c docs: Port all docstring to gtk-doc markdown 2019-04-26 20:32:26 -04:00
gstrtspwms.h Fix FSF address 2012-11-03 20:40:37 +00:00
meson.build docs: Port documentation to hotdoc 2019-05-13 17:00:00 -04:00
README ext/jpeg/gstjpegdec.c: Make jpegdec quiet on MJPEG decoding 2005-01-10 22:00:15 +00:00

README 

ASF Demuxer Plugin
==================

Overview
--------

This plugin is a demuxer for Microsoft's ASF Advanced Streaming Format
or ASF [1]. This demuxer only supports ASF v1.0 since the vast
majority of existing ASF files use that version. The specification
has been derived from a third party source [2] without reference to
the original.

Design
------

The ASF format can carry any combination of audio, video or
'ASF_Command_Media' streams. For simplicity it is assumed that each
file can carry up to 16 audio streams and 16 video streams. These are
implemented as dynamic pads and appear as appropriate once the file
headers have been parsed.

    (-------------------------)
    ! asfdemux                !
    !                    (video/raw0)---
    !                    (video/raw1)---
    !                    (video/raw...
  --- src                     !
    !                    (audio/raw0)---
    !                    (audio/raw1)---
    !                    (audio/raw...
    !                         !
    (-------------------------)


Known stream fourccs are:

Type		Tags		MIME type
------------------------------------------
H263		H263 I263	video/x-h263
MJPEG		MJPG		image/jpeg	
MPEG4		DIVX divx DX50	video/mpeg
		XVID xvid mp4s	
		MP4S M4S2 m4s2
		0x04000000
MSMPEG4V1	MPG4		video/mpeg
MSMPEG4V2	MP42		video/mpeg
MSMPEG4V3	MP43 DIV3	video/mpeg
WMV1		WMV1		video/x-wmv, wmvversion = (int) 1
WMV2		WMV2		video/x-wmv, wmvversion = (int) 2
WMV3		WMV3		video/x-wmv, wmvversion = (int) 3
WMA1		WMA1		audio/x-wma, wmaversion = (int) 1
WMA2		WMA2		audio/x-wma, wmaversion = (int) 2
				audio/x-wma, wmaversion = (int) 3

These video stream headers is very similar to that used in the AVI
format as are the audio stream headers. In addition the content types
are basically the same also so, for compatibility with existing
plugins the src pads are set up as video/x-msvideo. This enables
compatibility with the ffmpeg plugin.

The demuxing process begins with the loop function gst_asf_demux_loop
and parses the file in a recursive tree as follows:

	gst_asf_demux_loop()
	+-> gst_asf_demux_process_object()   <----
	    +-> gst_asf_demux_process_stream()    \
	    |-> gst_asf_demux_process_file()      |
	    |-> gst_asf_demux_process_header()  --+
	    |-> gst_asf_demux_process_data()
		+-> gst_asf_demux_process_segment()
		    +-> gst_asf_demux_process_chunk()

Todo
----

- Support for ASF v2.0
- Support for command media streams



References
----------

[1] Microsoft. ASF Specification - Windows Media Technologies. 
http://www.microsoft.com/windows/windowsmedia/format/asfspec.aspx (v01.20.01e, September 2003)

[2] divx at euro.ru. ASF format version 1.0,
reconstruction. http://avifile.sourceforge.net/asf-1.0.htm