avcodec: add a native SMPTE VC-2 HQ encoder

This commit adds a new encoder capable of creating BBC/SMPTE Dirac/VC-2 HQ
profile files.

Dirac is a wavelet based codec created by the BBC a little more than 10
years ago. Since then, wavelets have mostly gone out of style as they
did not provide adequate encoding gains at lower bitrates. Dirac was a
fully featured video codec equipped with perceptual masking, support for
most popular pixel formats, interlacing, overlapped-block motion
compensation, and other features. It found new life after being stripped
of various features and standardized as the VC-2 codec by the SMPTE with
an extra profile, the HQ profile that this encoder supports, added.

The HQ profile was based off of the Low-Delay profile previously
existing in Dirac. The profile forbids DC prediction and arithmetic
coding to focus on high performance and low delay at higher bitrates.
The standard bitrates for this profile vary but generally 1:4
compression is expected (~525 Mbps vs the 2200 Mbps for uncompressed
1080p50). The codec only supports I-frames, hence the high bitrates.

The structure of this encoder is simple: do a DWT transform on the
entire image, split it into multiple slices (specified by the user) and
encode them in parallel. All of the slices are of the same size, making
rate control and threading very trivial. Although only in C, this encoder
is capable of 30 frames per second on an 4 core 8 threads Ivy Bridge.
A lookup table is used to encode most of the coefficients.

No code was used from the GSoC encoder from 2007 except for the 2
transform functions in diracenc_transforms.c. All other code was written
from scratch.

This encoder outperforms any other encoders in quality, usability and in
features. Other existing implementations do not support 4 level
transforms or 64x64 blocks (slices), which greatly increase compression.

As previously said, the codec is meant for broadcasting, hence support
for non-broadcasting image widths, heights, bit depths, aspect ratios,
etc. are limited by the "level". Although this codec supports a few
chroma subsamplings (420, 422, 444), signalling those is generally
outside the specifications of the level used (3) and the reference
decoder will outright refuse to read any image with such a flag
signalled (it only supports 1920x1080 yuv422p10). However, most
implementations will happily read files with alternate dimensions,
framerates and formats signalled.

Therefore, in order to encode files other than 1080p50 yuv422p10le, you
need to provide an "-strict -2" argument to the command line. The FFmpeg
decoder will happily read any files made with non-standard parameters,
dimensions and subsamplings, and so will other implementations. IMO this
should be "-strict -1", but I'll leave that up for discussion.

There are still plenty of stuff to implement, for instance 5 more
wavelet transforms are still in the specs and supported by the decoder.

The encoder can be lossless, given a high enough bitrate.

Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

1 files changed, 229 insertions, 0 deletions

diff --git a/libavcodec/vc2enc_dwt.c b/libavcodec/vc2enc_dwt.c
new file mode 100644
index 0000000000..eb341684cd
--- /dev/null
+++ b/libavcodec/vc2enc_dwt.c
@@ -0,0 +1,229 @@
+/*
+ * Copyright (C) 2007 Marco Gerards <marco@gnu.org>
+ * Copyright (C) 2016 Open Broadcast Systems Ltd.
+ * Author        2016 Rostislav Pehlivanov <atomnuker@gmail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/attributes.h"
+#include "libavutil/mem.h"
+#include "vc2enc_dwt.h"
+
+/* Since the transforms spit out interleaved coefficients, this function
+ * rearranges the coefficients into the more traditional subdivision,
+ * making it easier to encode and perform another level. */
+static av_always_inline void deinterleave(dwtcoef *linell, ptrdiff_t stride,
+                                          int width, int height, dwtcoef *synthl)
+{
+    int x, y;
+    ptrdiff_t synthw = width << 1;
+    dwtcoef *linehl = linell + width;
+    dwtcoef *linelh = linell + height*stride;
+    dwtcoef *linehh = linelh + width;
+
+    /* Deinterleave the coefficients. */
+    for (y = 0; y < height; y++) {
+        for (x = 0; x < width; x++) {
+            linell[x] = synthl[(x << 1)];
+            linehl[x] = synthl[(x << 1) + 1];
+            linelh[x] = synthl[(x << 1) + synthw];
+            linehh[x] = synthl[(x << 1) + synthw + 1];
+        }
+        synthl += synthw << 1;
+        linell += stride;
+        linelh += stride;
+        linehl += stride;
+        linehh += stride;
+    }
+}
+
+static void vc2_subband_dwt_97(VC2TransformContext *t, dwtcoef *data,
+                               ptrdiff_t stride, int width, int height)
+{
+    int x, y;
+    dwtcoef *datal = data, *synth = t->buffer, *synthl = synth;
+    const ptrdiff_t synth_width  = width  << 1;
+    const ptrdiff_t synth_height = height << 1;
+
+    /*
+     * Shift in one bit that is used for additional precision and copy
+     * the data to the buffer.
+     */
+    for (y = 0; y < synth_height; y++) {
+        for (x = 0; x < synth_width; x++)
+            synthl[x] = datal[x] << 1;
+        synthl += synth_width;
+        datal += stride;
+    }
+
+    /* Horizontal synthesis. */
+    synthl = synth;
+    for (y = 0; y < synth_height; y++) {
+        /* Lifting stage 2. */
+        synthl[1] -= (8*synthl[0] + 9*synthl[2] - synthl[4] + 8) >> 4;
+        for (x = 1; x < width - 2; x++)
+            synthl[2*x + 1] -= (9*synthl[2*x] + 9*synthl[2*x + 2] - synthl[2*x + 4] -
+                                synthl[2 * x - 2] + 8) >> 4;
+        synthl[synth_width - 1] -= (17*synthl[synth_width - 2] -
+                                    synthl[synth_width - 4] + 8) >> 4;
+        synthl[synth_width - 3] -= (8*synthl[synth_width - 2] +
+                                    9*synthl[synth_width - 4] -
+                                    synthl[synth_width - 6] + 8) >> 4;
+        /* Lifting stage 1. */
+        synthl[0] += (synthl[1] + synthl[1] + 2) >> 2;
+        for (x = 1; x < width - 1; x++)
+            synthl[2*x] += (synthl[2*x - 1] + synthl[2*x + 1] + 2) >> 2;
+
+        synthl[synth_width - 2] += (synthl[synth_width - 3] +
+                                    synthl[synth_width - 1] + 2) >> 2;
+        synthl += synth_width;
+    }
+
+    /* Vertical synthesis: Lifting stage 2. */
+    synthl = synth + synth_width;
+    for (x = 0; x < synth_width; x++)
+        synthl[x] -= (8*synthl[x - synth_width] + 9*synthl[x + synth_width] -
+                      synthl[x + 3 * synth_width] + 8) >> 4;
+
+    synthl = synth + (synth_width << 1);
+    for (y = 1; y < height - 2; y++) {
+        for (x = 0; x < synth_width; x++)
+            synthl[x + synth_width] -= (9*synthl[x] +
+                                        9*synthl[x + 2 * synth_width] -
+                                        synthl[x - 2 * synth_width] -
+                                        synthl[x + 4 * synth_width] + 8) >> 4;
+        synthl += synth_width << 1;
+    }
+
+    synthl = synth + (synth_height - 1) * synth_width;
+    for (x = 0; x < synth_width; x++) {
+        synthl[x] -= (17*synthl[x - synth_width] -
+                      synthl[x - 3*synth_width] + 8) >> 4;
+                      synthl[x - 2*synth_width] -= (9*synthl[x - 3*synth_width] +
+                      8*synthl[x - 1*synth_width] - synthl[x - 5*synth_width] + 8) >> 4;
+    }
+
+    /* Vertical synthesis: Lifting stage 1. */
+    synthl = synth;
+    for (x = 0; x < synth_width; x++)
+        synthl[x] += (synthl[x + synth_width] + synthl[x + synth_width] + 2) >> 2;
+
+    synthl = synth + (synth_width << 1);
+    for (y = 1; y < height - 1; y++) {
+        for (x = 0; x < synth_width; x++)
+            synthl[x] += (synthl[x - synth_width] + synthl[x + synth_width] + 2) >> 2;
+        synthl += synth_width << 1;
+    }
+
+    synthl = synth + (synth_height - 2) * synth_width;
+    for (x = 0; x < synth_width; x++)
+        synthl[x] += (synthl[x - synth_width] + synthl[x + synth_width] + 2) >> 2;
+
+    deinterleave(data, stride, width, height, synth);
+}
+
+static void vc2_subband_dwt_53(VC2TransformContext *t, dwtcoef *data,
+                               ptrdiff_t stride, int width, int height)
+{
+    int x, y;
+    dwtcoef *synth = t->buffer, *synthl = synth, *datal = data;
+    const ptrdiff_t synth_width  = width  << 1;
+    const ptrdiff_t synth_height = height << 1;
+
+    /*
+     * Shift in one bit that is used for additional precision and copy
+     * the data to the buffer.
+     */
+    for (y = 0; y < synth_height; y++) {
+        for (x = 0; x < synth_width; x++)
+            synthl[x] = datal[x] << 1;
+        synthl += synth_width;
+        datal  += stride;
+    }
+
+    /* Horizontal synthesis. */
+    synthl = synth;
+    for (y = 0; y < synth_height; y++) {
+        /* Lifting stage 2. */
+        for (x = 0; x < width - 1; x++)
+            synthl[2 * x + 1] -= (synthl[2 * x] + synthl[2 * x + 2] + 1) >> 1;
+
+        synthl[synth_width - 1] -= (2*synthl[synth_width - 2] + 1) >> 1;
+
+        /* Lifting stage 1. */
+        synthl[0] += (2*synthl[1] + 2) >> 2;
+        for (x = 1; x < width - 1; x++)
+            synthl[2 * x] += (synthl[2 * x - 1] + synthl[2 * x + 1] + 2) >> 2;
+
+        synthl[synth_width - 2] += (synthl[synth_width - 3] + synthl[synth_width - 1] + 2) >> 2;
+
+        synthl += synth_width;
+    }
+
+    /* Vertical synthesis: Lifting stage 2. */
+    synthl = synth + synth_width;
+    for (x = 0; x < synth_width; x++)
+        synthl[x] -= (synthl[x - synth_width] + synthl[x + synth_width] + 1) >> 1;
+
+    synthl = synth + (synth_width << 1);
+    for (y = 1; y < height - 1; y++) {
+        for (x = 0; x < synth_width; x++)
+            synthl[x + synth_width] -= (synthl[x] + synthl[x + synth_width * 2] + 1) >> 1;
+        synthl += (synth_width << 1);
+    }
+
+    synthl = synth + (synth_height - 1) * synth_width;
+    for (x = 0; x < synth_width; x++)
+        synthl[x] -= (2*synthl[x - synth_width] + 1) >> 1;
+
+    /* Vertical synthesis: Lifting stage 1. */
+    synthl = synth;
+    for (x = 0; x < synth_width; x++)
+        synthl[x] += (2*synthl[synth_width + x] + 2) >> 2;
+
+    synthl = synth + (synth_width << 1);
+    for (y = 1; y < height - 1; y++) {
+        for (x = 0; x < synth_width; x++)
+            synthl[x] += (synthl[x + synth_width] + synthl[x - synth_width] + 2) >> 2;
+        synthl += (synth_width << 1);
+    }
+
+    synthl = synth + (synth_height - 2)*synth_width;
+    for (x = 0; x < synth_width; x++)
+        synthl[x] += (synthl[x - synth_width] + synthl[x + synth_width] + 2) >> 2;
+
+
+    deinterleave(data, stride, width, height, synth);
+}
+
+av_cold int ff_vc2enc_init_transforms(VC2TransformContext *s, int p_width, int p_height)
+{
+    s->vc2_subband_dwt[VC2_TRANSFORM_9_7]    = vc2_subband_dwt_97;
+    s->vc2_subband_dwt[VC2_TRANSFORM_5_3]    = vc2_subband_dwt_53;
+
+    s->buffer = av_malloc(2*p_width*p_height*sizeof(dwtcoef));
+    if (!s->buffer)
+        return 1;
+
+    return 0;
+}
+
+av_cold void ff_vc2enc_free_transforms(VC2TransformContext *s)
+{
+    av_freep(&s->buffer);
+}