BassWmaBASS_WMA_StreamCreateFile Method (String, Int64, Int64, BASSFlag)

public static int BASS_WMA_StreamCreateFile(
	string file,
	long offset,
	long length,
	BASSFlag flags
)

Public Shared Function BASS_WMA_StreamCreateFile ( 
	file As String,
	offset As Long,
	length As Long,
	flags As BASSFlag
) As Integer

Parameters

file

Type: SystemString
Filename or URL for which a stream should be created.

offset

Type: SystemInt64
File offset to begin streaming from (Unused, set to 0).

length

Type: SystemInt64
Data length... 0 = use all data up to the end of the file.

flags

Type: Un4seen.BassBASSFlag
Any combination of these flags: see BASSFlag.

Return Value

Use BASS_ChannelGetInfo(Int32, BASS_CHANNELINFO) to retrieve information on the format (sample rate, resolution, channels) of the stream. The bitrate (amongst other things) can be retrieved through BASS_ChannelGetTags(Int32, BASSTag) (BASS_TAG_WMA). When retrieving tags, a pointer to a series of null-terminated UTF-8 strings is returned, the final string ending with a double null.

A description of the codec used by the file is also available from BASS_ChannelGetTags(Int32, BASSTag) (BASS_TAG_WMA_CODEC). 2 null-terminated UTF-8 strings are returned, with the 1st string being the name of the codec, and the 2nd containing additional information like what VBR setting was used.

The playback length of the stream can be retrieved using BASS_ChannelGetLength(Int32, BASSMode). Until the whole file has been streamed, whatever length the file's header says is returned, which may or may not be exact.

Although the Windows Media modules uses its own internet streaming routines (not BASS's), the BASS_CONFIG_NET_PROXY and BASS_CONFIG_NET_TIMEOUT config options do have effect when opening WMA streams. When the BASS_CONFIG_NET_PLAYLIST config option is enabled, BASSWMA will process ASX and WPL files. None of the other NET config options apply.

Unless the BASS_CONFIG_WMA_BASSFILE config option is enabled, the Windows Media modules uses its own file reading routines, and the offset and length parameters are ignored, except that length is still the length when playing from memory. Also, BASS_StreamGetFilePosition(Int32, BASSStreamFilePosition) isn't fully supported. The file size (BASS_FILEPOS_END) can be retrieved, but the decode position (BASS_FILEPOS_CURRENT) is not available. The download progress of streamed files (BASS_FILEPOS_DOWNLOAD) can also be retrieved. The buffering progress (percentage) can be retrieved using the BASS_FILEPOS_WMA_BUFFER mode.

When streaming a file from the internet, it's not possible to seek with BASS_ChannelSetPosition(Int32, Int64, BASSMode) until the whole file has been downloaded. A sync (BASS_SYNC_DOWNLOAD) can be set to be notified when the file has been downloaded.

With Windows Media versions prior to 9 (and when streaming from the internet), WMA decoding is performed in a separate thread, so the CPU used to decode a file/stream during playback will not be included in the BASS_GetCPU return value.

When using the BASS_STREAM_DECODE flag, it's not possible to play the stream. Because the decoded sample data is not outputted, "decoding channels" can still be used when there is no output device (using the "no sound" device with BASS_Init(Int32, Int32, BASSInit, IntPtr, IntPtr)).

The playback rate of local files can be altered with BASS_ChannelSetAttribute(Int32, BASSAttribute, Single). But the playback rate of internet streams should not be changed, because they are decoded at a fixed rate - the rate required to sustain playback at normal speed. So increasing the rate will result in playback stalling.

Using VBR, lossless and multi-channel WMA files/streams requires Windows Media 9 to be installed.

Reference