mirror of https://bitbucket.org/ausocean/av.git
111 lines
3.8 KiB
Go
111 lines
3.8 KiB
Go
/*
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DESCRIPTION
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decode.go provides slice decoding functionality.
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AUTHORS
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Saxon A. Nelson-Milton <saxon@ausocean.org>
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LICENSE
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Copyright (C) 2019 the Australian Ocean Lab (AusOcean).
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It is free software: you can redistribute it and/or modify them
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under the terms of the GNU General Public License as published by the
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Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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It is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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in gpl.txt. If not, see http://www.gnu.org/licenses.
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*/
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package h264dec
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// picOrderCntType0 is used to return topFieldOrderCnt and bottomFieldOrderCnt
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// when pic_order_cnt_type i.e vid.PicOrderCntType == 0, using the process
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// defined in section 8.2.1.1 of the specifications. If topFieldOrderCnt or
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// bottomFieldOrderCnt are -1 they are unset.
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func picOrderCntType0(vid *VideoStream, ctx SliceContext) (topFieldOrderCnt, bottomFieldOrderCnt int) {
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prevPicOrderCntMsb, prevPicOrderCntLsb := 0, 0
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topFieldOrderCnt, bottomFieldOrderCnt = -1, -1
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// NB: We're currently only handling IDRs so panic.
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if !vid.idrPicFlag {
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panic("not implemented")
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}
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switch {
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case (ctx.PicOrderCntLsb < prevPicOrderCntLsb) && ((prevPicOrderCntLsb - ctx.PicOrderCntLsb) >= (vid.maxPicOrderCntLsb / 2)):
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vid.picOrderCntMsb = prevPicOrderCntMsb + vid.maxPicOrderCntLsb
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case (ctx.PicOrderCntLsb > prevPicOrderCntLsb) && ((ctx.PicOrderCntLsb - prevPicOrderCntLsb) > (vid.maxPicOrderCntLsb / 2)):
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vid.picOrderCntMsb = prevPicOrderCntMsb - vid.maxPicOrderCntLsb
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default:
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vid.picOrderCntMsb = prevPicOrderCntMsb
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}
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if !ctx.BottomField {
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topFieldOrderCnt = vid.picOrderCntMsb + ctx.PicOrderCntLsb
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} else {
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if !ctx.FieldPic {
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bottomFieldOrderCnt = topFieldOrderCnt + ctx.DeltaPicOrderCntBottom
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} else {
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bottomFieldOrderCnt = vid.picOrderCntMsb + ctx.PicOrderCntLsb
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}
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}
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return
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}
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// picOrderCntType1 is used to return topFieldOrderCnt and bottomFieldOrderCnt
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// when vic.PicOrderCntType == 1 according to logic defined in section 8.2.1.2
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// of the specifications. If topFieldOrderCnt or bottomFieldOrderCnt are -1,
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// then they are considered unset.
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func picOrderCntType1(vid VideoStream, ctx SliceContext) (topFieldOrderCnt, bottomFieldOrderCnt int) {
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topFieldOrderCnt, bottomFieldOrderCnt = -1, -1
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// TODO: this will be prevFrameNum when we do frames other than IDR.
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_ = vid.priorPic.FrameNum
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if vid.idrPicFlag {
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vid.frameNumOffset = 0
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} else {
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panic("not implemented")
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}
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absFrameNum := 0
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if ctx.NumRefFramesInPicOrderCntCycle != 0 {
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absFrameNum = vid.frameNumOffset + ctx.FrameNum
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}
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if ctx.RefIdc == 0 && absFrameNum > 0 {
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absFrameNum = absFrameNum - 1
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}
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var expectedPicOrderCnt int
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if absFrameNum > 0 {
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picOrderCntCycleCnt := (absFrameNum - 1) / int(ctx.NumRefFramesInPicOrderCntCycle)
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frameNumInPicOrderCntCycle := (absFrameNum - 1) % int(ctx.NumRefFramesInPicOrderCntCycle)
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expectedPicOrderCnt = picOrderCntCycleCnt * vid.expectedDeltaPerPicOrderCntCycle
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for i := 0; i <= frameNumInPicOrderCntCycle; i++ {
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expectedPicOrderCnt = expectedPicOrderCnt + ctx.OffsetForRefFrameList[i]
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}
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}
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if ctx.RefIdc == 0 {
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expectedPicOrderCnt = expectedPicOrderCnt + int(ctx.OffsetForNonRefPic)
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}
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switch {
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case !ctx.FieldPic:
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topFieldOrderCnt = expectedPicOrderCnt + ctx.DeltaPicOrderCnt[0]
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bottomFieldOrderCnt = topFieldOrderCnt + int(ctx.OffsetForTopToBottomField) + ctx.DeltaPicOrderCnt[1]
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case !ctx.BottomField:
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topFieldOrderCnt = expectedPicOrderCnt + ctx.DeltaPicOrderCnt[0]
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default:
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bottomFieldOrderCnt = expectedPicOrderCnt + int(ctx.OffsetForTopToBottomField) + ctx.DeltaPicOrderCnt[0]
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}
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return
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}
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