mirror of
https://github.com/mpv-player/mpv
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b4d938165e
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@10070 b3059339-0415-0410-9bf9-f77b7e298cf2
159 lines
4.2 KiB
Plaintext
159 lines
4.2 KiB
Plaintext
all audio codecs (cook,atrk,14_4,28_8,dnet,sipr) have the same interface,
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but i have only analyzed the cook codec
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audio properties (hex)
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00 short text/description of the format (bitrate, when to use)
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01 bitrate (bits/s) //avg. bytes/sec output
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02 ulong: ?
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ulong: samples per second
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ushort: bits/sample
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ushort: number of channels
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03 same as 02 //constant 2
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04 long description
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05 constant 1 (always?)
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06 ulong: block align (input frame size for RADecode)
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07 string: minimum player version
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08 n/a
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09 n/a
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0A n/a
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0B n/a
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0C n/a
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0D ?
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0E ? leaf size
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0F ?
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10 ?
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11 ?
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12 ?
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13 min. output buffer size? max. number of samples?
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14 ?
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functions:
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ulong result=RAOpenCodec2(ra_main_t *raMain);
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ulong result=RAInitDecoder(ra_main_t *raMain, ra_init_struct *raInit);
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struct ra_init_struct {
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ulong sample_rate;
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ushort bits_per_sample; // unused by RAInitDecoder
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ushort number_of_channels;
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ushort unknown1; // 0
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ushort unknown2; // also unused (100)
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ulong leaf_size; // leaf size (used for interleaving, but
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// exists in audio stream description header (ASDH))
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ulong block_align; // packet size
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ulong bits_per_sample; // unused (always 16)
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char *ext_data; // 16 bytes located at the end of the
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// ASDH
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};
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There are some information missing that you usually need for playback,
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like bits per sample (the fileds aren't read by RAInitDecoder()). These
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are hard coded in the "flavors", i.e. the sub formats. A flavor is an entry
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in the list of available format variations like bitrate, number of channels,
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decoding algorithm, and so on.We can get those information with the
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following command:
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void *GetRAFlavorProperty(ra_main_t *raMain, ulong flavor, ulong property,
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short *property_length_in_bytes);
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returns property data for a specific data
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This is not important, because it's just a read only function.
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These flavor properties don't seem to exist in
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ulong RADecode(ra_main_t *raMain, char *input_buffer,
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ulong input_buffer_size, char *output_buffer,
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ulong *decoded_bytes, ulong p6=-1);
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RAFreeDecoder(ra_main_t *);
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RACloseCodec(ra_main_t *);
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ulong RASetFlavor(ra_main_t *ra_main, ulong flavor);
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Set the flavor of the stream.
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a flavor is an entry in the list of available format variations like
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bitrate, number of channels, decoding algorithm, and so on
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audio data storage:
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-------------------
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With Real Audio V5 (or earlier?), the audio streams can be interleaved,
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i.e. the stream is striped amongst several data packets. The packets
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(which have a fixed size packet_len) are split up into a fixed number
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of num_parts equally sized parts - I call them leaves in lack of
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better name. The leaves have the size leaf_size = packet_len / num_parts.
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To create a bunch of packets, you need 2*num_parts stream packets.
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The first part of the first stream packet is stored in leaf number 0,
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the first part of the second into leaf number num_parts, the one of the
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next one into leaf number 1 etc. The following part of a stream packet
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is stored 2*num_packets behind the current part of the same stream packet.
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In short words: when you have a matrix with the leaves as the values,
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it's a transposition in conjunction with a permutation.
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packet | leaf | stream packet, part no.
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-------+---------------+------------------------
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0 | 0 | (0,0)
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0 | 1 | (2,0)
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. | . | .
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. | . | .
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0 | num_parts-1 | (2*num_parts-2,0)
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0 | num_parts | (1,0)
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0 | num_parts+1 | (3,0)
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. | . | .
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. | . | .
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0 | 2*num_parts-1 | (2*num_parts-1,0)
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1 | 0 | (0,1)
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. | . | .
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. | . | .
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sequence of calls:
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------------------
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RAOpenCodec2()
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RAInitDecoder()
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RASetFlavor()
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RAGetFlavorProperty(0xE)
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sequence of RADecode()s
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once a RAGetFlavorProperty(0xE) after some RADecode()s
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and occasionally the following sequence:
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RAGetFlavorProperty(0)
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RAGetFlavorProperty(7)
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which is rather pointless because they only return
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cleartext audio descriptions
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RAFreeDecoder()
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RACloseCodec()
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RAFlush(ra_main_t *raMain, char *output_buffer, ulong *retval)
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will be called when seeking
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output_buffer points to the output buffer from the last
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decode operation.
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retval is unknown, returning always 0x18 in a specific sample
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-> further investigation needed
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