EA MAD文件格式分析

legojohn

之前lrdcq也发过关于MAD的文件格式，点我
今天在逛ST SM论坛，无意的发现了以下的东西

来自：http://wiki.multimedia.cx/index.php?title=Electronic_Arts_MAD
          有兴趣想研究其他格式的可以来这里看
          http://wiki.multimedia.cx/index.php?title=Electronic_Arts_Formats

正文：





MAD is a video codec used in various games published by companies under the Electronic Arts umbrella. The codec is an evolution of the earlier TGQ and TQI codecs, adding motion compensation and low-quality frame concepts. MAD is an abbreviation for "Madcow Movie".


See Electronic Arts Formats for file format description. Each MADk, MADm and MADe chunk corresponds to a video frame, where MADk is an intra-frame, MADm is an inter-frame and MADe is a low-quality-inter frame. Low-quality-inter frames are identical to inter frames, but are not used for motion compensation and are discarded immediately after presentation. Each frame is divided into 16x16 pixel macroblocks, with each macroblock further divided into with four 8x8 luma and two half-resolution 8x8 chroma blocks. Standard MPEG-1 block ordering is used.
Each chunk begins with a 16 byte header, followed by a bitstream. Symbols within the header are encoded using 16-bit little-endian most-to-least-significant bit packing. <FIXME: explain bit packing>. Although frame type is reported within the header, the field is not valid in some samples, and is therefore unreliable. Frame type should be inferred from the chunk type.

1. 
   
2.    Offset   Data_type   Name         Description
   
3.    0x0000   four bytes  unknown      always zero
   
4.    0x0000   le_u16      unknown
   
5.    0x0006   le_u16      frame_rate   milliseconds per frame
   
6.    0x0008   le_u16      width        image width (pixels)
   
7.    0x000a   le_u16      height       image height (pixels)
   
8.    0x000c   u8          unknown
   
9.    0x000d   u8          quantizer    frame quantizer
   
10.    0x000e   u8          frame_type   not valid for all samples
    
11.    0x000f   u8          unknown
    
12.    for each vertical macroblock
    
13.        for each horizontal macroblock
    
14.            decode_mb

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Macroblock composition is based on a 6-bit block type, where each bit indicates the type of an 8x8 block within macroblock. The least-significant-bit corresponds to the first block. A clear bit indicates an intra-block, and a set bit indicates a motion-compensated block.
For intra frames, the block type is assumed to be all clear. For inter and low-quality inter frames, the block type is derived from a VLC. If the block type is none zero, then a full-pel motion vector is read from the bitstream. A description of the block_type VLC and decoding algorithm is provided below.

1. if (intra frame)
   
2. block_type = 000000b
   
3. else // inter or low-quality-inter frame
   
4. switch get_vlc()
   
5. case 1b : block_type = 111111b
   
6. case 01b : block_type = get_bits(6);
   
7. case 00b : block_type = 000000b
   
8. 
   
9. if (block_type != 0)
   
10. x = GetVector();
    
11. y = GetVector();
    
12. 
    
13. for i = 0 through 5 // for each block
    
14. if block_type & (1<<I)
    
15. mc_offset = GetVector()
    
16. motion_compensation
    
17. else
    
18. decode_coeffs

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Full-pel 8x8 block motion compensation is performed using the motion vector. Following the compensation step, each pixel in the block is offset by the mc_offset value and clipped to 0, 255.



Vector values are read from the bitstream using the following algorithm.

1.     value = 0
   
2.    if (get_bits(1))
   
3.        if (get_bits(1))
   
4.            value = -17
   
5.        value += get_bits(4) + 1

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All coefficients, including DC, are decoded using the MPEG-1 AC run-length VLC technique. The RLVLC table is identical to that used for the TGQ codec and coefficients are ordered using the EA zigzag scan pattern. Dequantization is performed by multiplying the coefficients by a dequantization table. This table is calculated for each frame using the frame quantizer.

1.     dequant_table[0] = base_table[0] * base_table2[0]
   
2.    for i equals 0 through 63
   
3.        dequant_table = (base_table*base_table2*frame_quant + 4) / 8
   
4. 
   
5.    where base_table and base_table2 are defined in TGQ and TQI respectively.

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[ 本帖最后由 legojohn 于 2010-1-27 16:47 编辑 ]

情感的禁区

不懂 好深奥啊

孙大炮

都英语的看不懂

Moen

得特别说明没事不要看XD

天唐永thianz

看不懂。
本想說能否有將地圖改得更大的希望  不過應是我妄想

ABITsa

SC4系统的极限能挖掘的现在基本都挖掘到了吧......

rszxh

我相信这个经过编译了……

legojohn

原帖由 天唐永thianz 于 2010/1/27 23:04 发表
看不懂。
本想說能否有將地圖改得更大的希望  不過應是我妄想

地图？
SC4的这仅有的两个MAD不是开头“EA Games"和SC4游戏的动画么？

又不是开源，就是MAD格式标准......

仔细看一下,第一行开头写的是“Mad is a video..."
话说LSSS有没有仔细看呢

[ 本帖最后由 legojohn 于 2010-1-28 18:16 编辑 ]