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git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@20907 b3059339-0415-0410-9bf9-f77b7e298cf2
57 lines
2.5 KiB
Plaintext
57 lines
2.5 KiB
Plaintext
6. libao2: this control audio playing
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As in libvo (see 5.) also here are some drivers, based on the same API:
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static int control(int cmd, int arg);
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This is for reading/setting driver-specific and other special parameters.
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Not really used for now.
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static int init(int rate,int channels,int format,int flags);
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The init of driver, opens device, sets sample rate, channels, sample format
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parameters.
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Sample format: usually AFMT_S16_LE or AFMT_U8, for more definitions see
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dec_audio.c and linux/soundcards.h files!
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static void uninit();
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Guess what.
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Ok I help: closes the device, not (yet) called when exit.
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static void reset();
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Resets device. To be exact, it's for deleting buffers' contents,
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so after reset() the previously received stuff won't be output.
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(called if pause or seek)
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static int get_space();
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Returns how many bytes can be written into the audio buffer without
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blocking (making caller process wait). MPlayer occasionally checks the
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remaining space and tries to fill the buffer with play() if there's free
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space. The buffer size used should be sane; a buffer that is too small
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could run empty before MPlayer tries filling it again (normally once per
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video frame), a buffer that is too big would force MPlayer decode the file
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far ahead trying to find enough audio data to fill it.
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static int play(void* data,int len,int flags);
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Plays a bit of audio, which is received throught the "data" memory area, with
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a size of "len". It has to copy the data, because they can be overwritten
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after the call is made. Doesn't have to use all the bytes; it has to
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return the number of bytes used used (copied to buffer). If
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flags|AOPLAY_FINAL_CHUNK is true then this is the last audio in the file.
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The purpose of this flag is to tell aos that round down the audio played
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from "len" to a multiple of some chunksize that this "len" should not be
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rounded down to 0 or the data will never be played (as MPlayer will never
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call play() with a larger len).
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static float get_delay();
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Returns how long time it will take to play the data currently in the
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output buffer. Be exact, if possible, since the whole timing depends
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on this! In the worst case, return the maximum delay.
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!!! Because the video is synchronized to the audio (card), it's very important
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!!! that the get_delay function is correctly implemented!
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static void audio_pause(void);
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Pause playing but do not delete buffered data if possible.
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static void audio_resume(void);
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Continue playing after audio_pause().
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