Creates a sample stream from an ALAC file on the internet, optionally receiving the downloaded data in a callback.

    char *url,
    DWORD offset,
    DWORD flags,
    void *user


urlURL of the file to stream. Should begin with "http://" or "https://" or "ftp://".
offsetFile position to start streaming from. This is ignored by some servers, specifically when the file length is unknown.
flagsA combination of these flags.
BASS_SAMPLE_FLOATUse 32-bit floating-point sample data. See Floating-point channels for more info.
BASS_SAMPLE_SOFTWAREForce the stream to not use hardware mixing.
BASS_SAMPLE_3DEnable 3D functionality. This requires that the BASS_DEVICE_3D flag was specified when calling BASS_Init, and the stream must be mono. The SPEAKER flags can not be used together with this flag.
BASS_SAMPLE_LOOPLoop the file. This flag can be toggled at any time using BASS_ChannelFlags. This flag is ignored when streaming in blocks (BASS_STREAM_BLOCK).
BASS_SAMPLE_FXEnable the old implementation of DirectX 8 effects. See the DX8 effect implementations section for details. Use BASS_ChannelSetFX to add effects to the stream.
BASS_STREAM_RESTRATERestrict the download rate of the file to the rate required to sustain playback. If this flag is not used, then the file will be downloaded as quickly as the user's internet connection allows.
BASS_STREAM_BLOCKDownload and play the file in smaller chunks. Uses a lot less memory than otherwise, but it's not possible to seek or loop the stream; once it's ended, the file must be opened again to play it again. This flag will automatically be applied when the file length is unknown, for example with Shout/Icecast streams. This flag also has the effect of resticting the download rate.
BASS_STREAM_STATUSPass status info (HTTP/ICY tags) from the server to the DOWNLOADPROC callback during connection. This can be useful to determine the reason for a failure.
BASS_STREAM_AUTOFREEAutomatically free the stream when playback ends.
BASS_STREAM_DECODEDecode the sample data, without playing it. Use BASS_ChannelGetData to retrieve decoded sample data. The BASS_SAMPLE_3D, BASS_STREAM_AUTOFREE and SPEAKER flags can not be used together with this flag. The BASS_SAMPLE_SOFTWARE and BASS_SAMPLE_FX flags are also ignored.
BASS_SPEAKER_xxxSpeaker assignment flags. These flags have no effect when the stream is more than stereo.
BASS_UNICODEurl is in UTF-16 form. Otherwise it is ANSI on Windows or Windows CE, and UTF-8 on other platforms.
procCallback function to receive the file as it is downloaded... NULL = no callback.
userUser instance data to pass to the callback function.

Return value

If successful, the new stream's handle is returned, else 0 is returned. Use BASS_ErrorGetCode to get the error code.

Error codes

BASS_ERROR_INITBASS_Init has not been successfully called.
BASS_ERROR_NOTAVAILOnly decoding channels (BASS_STREAM_DECODE) are allowed when using the "no sound" device. The BASS_STREAM_AUTOFREE flag is also unavailable to decoding channels.
BASS_ERROR_NONETNo internet connection could be opened.
BASS_ERROR_ILLPARAMurl is not a valid URL.
BASS_ERROR_SSLSSL/HTTPS support is not available.
BASS_ERROR_TIMEOUTThe server did not respond to the request within the timeout period, as set with the BASS_CONFIG_NET_TIMEOUT config option.
BASS_ERROR_FILEOPENThe file could not be opened.
BASS_ERROR_FILEFORMThe file's format is not recognised/supported.
BASS_ERROR_FORMATThe sample format is not supported by the device/drivers. If the stream is more than stereo or the BASS_SAMPLE_FLOAT flag is used, it could be that they are not supported (ie. no WDM drivers).
BASS_ERROR_SPEAKERThe specified SPEAKER flags are invalid. The device/drivers do not support them, they are attempting to assign a stereo stream to a mono speaker or 3D functionality is enabled.
BASS_ERROR_MEMThere is insufficient memory.
BASS_ERROR_NO3DCould not initialize 3D support.
BASS_ERROR_MP4_NOSTREAMThe file cannot be streamed due to its MP4 atom order; "moov" should come before "mdat".
BASS_ERROR_UNKNOWNSome other mystery problem!


In order to stream an ALAC file, its "moov" atom must come before its "mdat" atom.

When playing the stream, BASS will stall the playback if there is insufficient data to continue playing. Playback will automatically be resumed when sufficient data has been downloaded. BASS_ChannelIsActive can be used to check if the playback is stalled, and the progress of the file download can be checked with BASS_StreamGetFilePosition.

When streaming in blocks (BASS_STREAM_BLOCK flag), be careful not to stop/pause the stream for too long, otherwise the connection may timeout due to there being no activity and the stream will end prematurely.

When using an offset, the file length returned by BASS_StreamGetFilePosition can be used to check that it was successful by comparing it with the original file length. Another way to check is to inspect the HTTP headers retrieved with BASS_ChannelGetTags.


Away from Windows, all mixing is done in software (by BASS), so the BASS_SAMPLE_SOFTWARE flag is unnecessary. The BASS_SAMPLE_FX flag is also ignored.

See also

BASS_ALAC_StreamCreateFile, BASS_ALAC_StreamCreateFileUser