BMediaDecoder¶
Constructor and Destructor¶
BMediaDecoder()
BMediaDecoder::BMediaDecoder()
BMediaDecoder::BMediaDecoder(const media_format *inFormat, const void *info = NULL, size_t infoSize = 0)
BMediaDecoder::BMediaDecoder(const media_codec_info *mci)
The constructor sets up the BMediaDecoder. If you use the empty
form of the constructor, you’ll have to call SetTo()
to establish the format to be decoded before
calling Decode()
.
The second form accepts a media_format
structure, inFormat, that indicates the type of media data that
will be input into the decoder. info, if specified, will be
filled out with text information about the node; you must specify a buffer
infoSize bytes long.
The third form of the constructor accepts a media_codec_info structure, mci, that determines which codec should be used.
Note
If you use either the media_format
or
media_codec_info form of the constructor, you must call
InitCheck()
to ensure that
construction was successful before using any other functions in this class.
~BMediaDecoder()
virtual BMediaDecoder::~BMediaDecoder()
Releases the decoder add-on being used by the BMediaDecoder.
Hook Functions¶
GetNextChunk()
status_t BMediaDecoder::GetNextChunk(const void **chunkData, size_t *chunkLen, media_header *mh)
In derived classes, you should implement this function to fetch the media
data from the source. Set chunkData to be a pointer to the next
chunk of media data, and chunkLen to the size of that buffer. The
media_header
structure mh provides
information you can use while fetching the chunk.
This hook is called by the decoder add-on in order to fetch the data from the source.
Return B_OK
if the chunk is fetched safely, or an
appropriate error code otherwise.
Member Functions¶
Decode()
status_t BMediaDecoder::Decode(void *outBuffer, int64 *frameCount, media_header *outMH, media_decode_info *info)
Decodes a chunk of media data into the output buffer specified by outBuffer. On return, outFrameCount is set to indicate how many frames of data were decoded, and outMH is the header for the decoded buffer.
The media_decode_info structure info is used on input to specify decoding parameters.
The amount of data decoded is part of the format determined by
SetTo()
or SetInputFormat()
. For audio, it’s the buffer size. For
video, it’s one frame, which is height*row_bytes. The data to be decoded
will be fetched from the source by the decoder add-on calling the derived
class’ GetNextChunk()
function.
Return Code |
Description |
---|---|
|
No error. |
|
The BMediaDecoder hasn’t been initialized. |
Other errors. |
The decoder’s Decode() function can return errors. |
GetDecoderInfo()
status_t BMediaDecoder::GetDecoderInfo(media_codec_info *outInfo) const
Fills out the media_codec_info structure outInfo with information about the decoder being used by the BMediaDecoder.
Return Code |
Description |
---|---|
|
No error. |
|
The BMediaDecoder hasn’t been initialized. |
Other errors. |
The decoder’s GetCodecInfo() function can return errors. |
InitCheck()
status_t BMediaDecoder::InitCheck() const
Returns a status_t value indicating whether or not construction was successful. You must call this function after construction before calling any other BMediaDecoder functions.
Return Code |
Description |
---|---|
|
The constructor was successful. |
Other errors. |
See |
SetInputFormat(), SetOutputFormat()
status_t BMediaDecoder::SetInputFormat(const media_format *inFormat, const void *info = NULL, size_t infoSize = 0)
status_t BMediaDecoder::SetOutputFormat(media_format *outputFormat)
SetInputFormat() sets the input data format to inFormat. On return, info (if you don’t specify NULL) is filled out by the decoder to contain whatever textual information the decoder wants to provide. infoSize must indicate the size of the buffer pointed to by info.
Unlike SetTo()
,
SetInputFormat() function does not select a codec, so the
currently-selected codec will continue to be used. You should only use
SetInputFormat() to refine the format settings if it will not
require the use of a different decoder.
SetOutputFormat() sets the format the decoder should output. On return, the outputFormat is changed to match the actual format that will be output; this can be different if you specified any wildcards.
Return Code |
Description |
---|---|
|
No error. |
|
The BMediaDecoder hasn’t been initialized yet. |
Other errors. |
The decoder’s Sniff(), Format(),and Reset() functions can return errors through SetInputFormat(). |
SetTo()
status_t BMediaDecoder::SetTo(const media_format *inFormat, const void *info = NULL, size_t infoSize = 0)
status_t BMediaDecoder::SetTo(const media_codec_info *mci)
SetTo() sets the format of media data that will be decoded by the BMediaDecoder object. This also causes the BMediaDecoder to locate an appropriate codec to use.
The first form accepts a media_format
structure, inFormat, that indicates the type of media data that
will be input into the decoder. info, if specified, will be
filled out with text information about the node; you must specify a buffer
infoSize bytes long.
The second form of SetTo() accepts a media_codec_info structure, mci, that determines which codec should be used.
Return Code |
Description |
---|---|
|
No error. |
|
The specified |
|
Something else went wrong. |
|
Unable to instantiate the decoder. |