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Diffstat (limited to 'contrib/ffmpeg/doc/snow.txt')
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1 files changed, 0 insertions, 259 deletions
diff --git a/contrib/ffmpeg/doc/snow.txt b/contrib/ffmpeg/doc/snow.txt deleted file mode 100644 index 4b8fab75a..000000000 --- a/contrib/ffmpeg/doc/snow.txt +++ /dev/null @@ -1,259 +0,0 @@ -============================================= -SNOW Video Codec Specification Draft 20070103 -============================================= - - -Definitions: -============ - -MUST the specific part must be done to conform to this standard -SHOULD it is recommended to be done that way, but not strictly required - -ilog2(x) is the rounded down logarithm of x with basis 2 -ilog2(0) = 0 - -Type definitions: -================= - -b 1-bit range coded -u unsigned scalar value range coded -s signed scalar value range coded - - -Bitstream syntax: -================= - -frame: - header - prediction - residual - -header: - keyframe b MID_STATE - if(keyframe || always_reset) - reset_contexts - if(keyframe){ - version u header_state - always_reset b header_state - temporal_decomposition_type u header_state - temporal_decomposition_count u header_state - spatial_decomposition_count u header_state - colorspace_type u header_state - chroma_h_shift u header_state - chroma_v_shift u header_state - spatial_scalability b header_state - max_ref_frames-1 u header_state - qlogs - } - - spatial_decomposition_type s header_state - qlog s header_state - mv_scale s header_state - qbias s header_state - block_max_depth s header_state - -qlogs: - for(plane=0; plane<2; plane++){ - quant_table[plane][0][0] s header_state - for(level=0; level < spatial_decomposition_count; level++){ - quant_table[plane][level][1]s header_state - quant_table[plane][level][3]s header_state - } - } - -reset_contexts - *_state[*]= MID_STATE - -prediction: - for(y=0; y<block_count_vertical; y++) - for(x=0; x<block_count_horizontal; x++) - block(0) - -block(level): - if(keyframe){ - intra=1 - y_diff=cb_diff=cr_diff=0 - }else{ - if(level!=max_block_depth){ - s_context= 2*left->level + 2*top->level + topleft->level + topright->level - leaf b block_state[4 + s_context] - } - if(level==max_block_depth || leaf){ - intra b block_state[1 + left->intra + top->intra] - if(intra){ - y_diff s block_state[32] - cb_diff s block_state[64] - cr_diff s block_state[96] - }else{ - ref_context= ilog2(2*left->ref) + ilog2(2*top->ref) - if(ref_frames > 1) - ref u block_state[128 + 1024 + 32*ref_context] - mx_context= ilog2(2*abs(left->mx - top->mx)) - my_context= ilog2(2*abs(left->my - top->my)) - mvx_diff s block_state[128 + 32*(mx_context + 16*!!ref)] - mvy_diff s block_state[128 + 32*(my_context + 16*!!ref)] - } - }else{ - block(level+1) - block(level+1) - block(level+1) - block(level+1) - } - } - - -residual: - FIXME - - - -Tag description: ----------------- - -version - 0 - this MUST NOT change within a bitstream - -always_reset - if 1 then the range coder contexts will be reset after each frame - -temporal_decomposition_type - 0 - -temporal_decomposition_count - 0 - -spatial_decomposition_count - FIXME - -colorspace_type - 0 - this MUST NOT change within a bitstream - -chroma_h_shift - log2(luma.width / chroma.width) - this MUST NOT change within a bitstream - -chroma_v_shift - log2(luma.height / chroma.height) - this MUST NOT change within a bitstream - -spatial_scalability - 0 - -max_ref_frames - maximum number of reference frames - this MUST NOT change within a bitstream - -ref_frames - minimum of the number of available reference frames and max_ref_frames - for example the first frame after a key frame always has ref_frames=1 - -spatial_decomposition_type - wavelet type - 0 is a 9/7 symmetric compact integer wavelet - 1 is a 5/3 symmetric compact integer wavelet - others are reserved - stored as delta from last, last is reset to 0 if always_reset || keyframe - -qlog - quality (logarthmic quantizer scale) - stored as delta from last, last is reset to 0 if always_reset || keyframe - -mv_scale - stored as delta from last, last is reset to 0 if always_reset || keyframe - FIXME check that everything works fine if this changes between frames - -qbias - dequantization bias - stored as delta from last, last is reset to 0 if always_reset || keyframe - -block_max_depth - maximum depth of the block tree - stored as delta from last, last is reset to 0 if always_reset || keyframe - -quant_table - quantiztation table - -Range Coder: -============ -FIXME - -Neighboring Blocks: -=================== -left and top are set to the respective blocks unless they are outside of -the image in which case they are set to the Null block - -top-left is set to the top left block unless its outside of the image in -which case it is set to the left block - -if this block has no larger parent block or its at the left side of its -parent block and the top right block is not outside of the image then the -top right block is used for top-right else the top-left block is used - -Null block -y,cb,cr are 128 -level, ref, mx and my are 0 - - -Motion Vector Prediction: -========================= -1. the motion vectors of all the neighboring blocks are scaled to -compensate for the difference of reference frames - -scaled_mv= (mv * (256 * (current_reference+1) / (mv.reference+1)) + 128)>>8 - -2. the median of the scaled left, top and top-right vectors is used as -motion vector prediction - -3. the used motion vector is the sum of the predictor and - (mvx_diff, mvy_diff)*mv_scale - - -Intra DC Predicton: -====================== -the luma and chroma values of the left block are used as predictors - -the used luma and chroma is the sum of the predictor and y_diff, cb_diff, cr_diff - - -Motion Compensation: -==================== -FIXME - -LL band prediction: -=================== -FIXME - -Dequantizaton: -============== -FIXME - -Wavelet Transform: -================== -FIXME - -TODO: -===== -Important: -finetune initial contexts -spatial_decomposition_count per frame? -flip wavelet? -try to use the wavelet transformed predicted image (motion compensated image) as context for coding the residual coefficients -try the MV length as context for coding the residual coefficients -use extradata for stuff which is in the keyframes now? -the MV median predictor is patented IIRC - -Not Important: -spatial_scalability b vs u (!= 0 breaks syntax anyway so we can add a u later) - - -Credits: -======== -Michael Niedermayer -Loren Merritt - - -Copyright: -========== -GPL + GFDL + whatever is needed to make this a RFC |