mpv/DOCS/tech/realcodecs/video-codecs.txt

The work has been based on the RV30 codec, but since RV20 has the same
interface, it might work for it as well.




error codes (the software uses redmond originated error codes)

1. internal code (1-10)
2. result

0    00000000 success
1    80004005 E_FAIL
2    8007000E E_OUTOFMEMORY
3,9  80004001 E_NOTIMPL
4,5  80070005 E_ACCESSDENIED
6    80004003 E_POINTER
7,10 80070057 E_INVALIDREG
8    80040FC1 (or 1FC?: CO_E_OBJISREG) - never occurred here





I think the only relevant file is the decoder drv[23].so.6.0
The rv[23]0 ones are just for streaming. We do this ourselves.


The codec consists of several functions. The relevant ones are:

RV20toYUV420Init()
RV20toYUV420Transform()
RV20toYUV420CustomMessage()
RV20toYUV420Free()


The others are irrelevant (seems to me). HiveMessage doesn't manipulate
anything and is only called in the beginning.

result=RV20toYUV420Init(struct init_data *, struct rvyuvMain **);

struct init_data {
	short constant=0xb;
	short width, height;
	short 0, 0, 0;
	ulong format1;
	long  1;
	ulong format2;
};

format1 and format2 are stored in the .rm file's stream headers.
(format1>>16)&3 seems to be a sub-codec id/selector, at least for rv30
it's the only difference between low and high bitrate files.

result=RV20toYUV420Transform(char *input_stream, char *output_data,
	struct transin *, struct transout *, struct rvyuvMain *);

struct transin {
	ulong length_of_input_data;
	ulong null;
	ulong num_sub_packets_in_block_minus_one;
	ulong *sub_packets_list;
	ulong another_null;
	ulong timestamp_from_stream;
};

struct transout {
	ulong flag1; // ((var_94&2!=0)&&(result==0))?1:0
	ulong flag2; // 4 LBS from var_94
	ulong zero;
	ulong width, height;
};

The length of output_stream is 1.5*width*height (I420 planar yuv 4:2:0).
input_stream is the exact data from the data block for one frame.

sub_packets_list is a list of num_sub_packets pairs of long values, in form:
1, 0,
1, offset_2nd,
1, offset_3rd,
1, offset_4th,
...

where offset_* are the offsets or sub-packets relative to input_stream.


result=RV20toYUV420CustomMessage(ulong *msg, struct rvyuvMain *);

Messages used by RV30:

A message is a triplet (cmd,val,ext) of ulong.

NOTE:
rv30 only requires the (0x24,2|3,{w,h,w,h}) message. others can be left out!
rv20 only requires the (0x11,2,0) message in rp8, before each transform call.

(3,2,0) 
returns always(?) an error, since a global variable inside the codec
(which points to a function similar to custommessage), is always NULL

(0x11,0|1|2,0)
val=0|1: sets intern2 to val, when intern1 is non-zero
         return 3 when intern1 is zero and val is 1
         else returns 0
val=2:   return intern2
what does intern[1,2] mean?

(0x12,...)
used by rv20, function unknown, can be ignored

(0x1e,2|3,1)
calls a subroutine and returns the result, purpose has to be detemined

(0x24,subcodec,{...})
copies 4 dwords to rvyuvMain+07c: { width, height, 0, 0 }
subcodec must be 2 (low-bitrate) or 3 (high-bitrate) for rv30.
the codec type (low vs high) can be determined from 1+((format1>>16)&3)
for rv20, this call should be ignored! (makes codec crashing)

(0x1c,a,b) - called inside transform
to be analyzed

(105,...)
used by rv20, function unknown, can be ignored


structure of rvyuvMain:
-----------------------

DWORDS (the entries are not always constant)
there are two w/h pairs at 05C. the first is the size of the
unscaled video stream, the second possibly image size

000	1	6	3	1
010	1	0	AEBFC0D1(magic)	0
020	0	ptr->?	0	0
030	0	0	->rvyuvMain+0x050	?
040	width	height	0x17	0x479
050	->rvyuvMain	0x17	0x17	width
060	height	width	height	0
070	0	1	0	0
080	0	0xb	w	h
090	w	h	0	0	
0A0	1	0xb0(w?)	0x58	0x58
0B0	ptr->?	0	0	1
0C0	0x32	1	0	0
0D0	0	0	0	0
0E0	0	0	0	0
0F0	0	0	0	0
100	0	0	0	0
110	p	p	p	p p are pointers to several function, for 
120	p	p	p	p example to the actual public functions
130	p	p	p	p (except init, the others are some kind of
140	p	p	p	p interfaces)
150	p	0	0	0
160	0	0x2000	1	0
170	0	0	0	0
180	1	1	0	0
190	0	0	0	0
1A0	0	0	0	0
1B0	1	0	ptr->?	ptr->?
1C0	1	0	0	0
1D0	0	0	0	0
1E0	0	0	0	0
...




Order of calls:
---------------

Init
(0x11,0,0)
(0x24,2,{...})

[
(3,2,0)->80004001
(0x11,1,0)
(0x1e,3,1)
Transform (internally calls (0x1c,x,y))
(11,2,0)
]

Free