proresenc: force bitrate not to exceed given limit

Apple ProRes Format Specifications mentions target data size for every frame,
so make sure frame meets it. This also allows encoder to demand much smaller
packet sizes for output.

libavcodec/proresenc.c

@@ -139,11 +139,14 @@ struct TrellisNode {
     int score;
 };
 
+#define MAX_STORED_Q 16
+
 typedef struct ProresContext {
     AVClass *class;
     DECLARE_ALIGNED(16, DCTELEM, blocks)[MAX_PLANES][64 * 4 * MAX_MBS_PER_SLICE];
     DECLARE_ALIGNED(16, uint16_t, emu_buf)[16*16];
-    int16_t quants[16][64];
+    int16_t quants[MAX_STORED_Q][64];
+    int16_t custom_q[64];
 
     ProresDSPContext dsp;
     ScanTable  scantable;
@@ -156,6 +159,8 @@ typedef struct ProresContext {
     int num_planes;
     int bits_per_mb;
 
+    int frame_size;
+
     int profile;
     const struct prores_profile *profile_info;
 
@@ -348,6 +353,15 @@ static int encode_slice(AVCodecContext *avctx, const AVFrame *pic,
     int slice_width_factor = av_log2(mbs_per_slice);
     int num_cblocks, pwidth;
     int plane_factor, is_chroma;
+    uint16_t *qmat;
+
+    if (quant < MAX_STORED_Q) {
+        qmat = ctx->quants[quant];
+    } else {
+        qmat = ctx->custom_q;
+        for (i = 0; i < 64; i++)
+            qmat[i] = ctx->profile_info->quant[i] * quant;
+    }
 
     for (i = 0; i < ctx->num_planes; i++) {
         is_chroma    = (i == 1 || i == 2);
@@ -373,7 +387,7 @@ static int encode_slice(AVCodecContext *avctx, const AVFrame *pic,
         sizes[i] = encode_slice_plane(ctx, pb, src, pic->linesize[i],
                                       mbs_per_slice, ctx->blocks[0],
                                       num_cblocks, plane_factor,
-                                      ctx->quants[quant]);
+                                      qmat);
         total_size += sizes[i];
     }
     return total_size;
@@ -500,6 +514,8 @@ static int find_slice_quant(AVCodecContext *avctx, const AVFrame *pic,
     int error, bits, bits_limit;
     int mbs, prev, cur, new_score;
     int slice_bits[TRELLIS_WIDTH], slice_score[TRELLIS_WIDTH];
+    int overquant;
+    uint16_t *qmat;
 
     mbs = x + mbs_per_slice;
 
@@ -526,7 +542,7 @@ static int find_slice_quant(AVCodecContext *avctx, const AVFrame *pic,
                        mbs_per_slice, num_cblocks[i]);
     }
 
-    for (q = min_quant; q <= max_quant; q++) {
+    for (q = min_quant; q < max_quant + 2; q++) {
         ctx->nodes[trellis_node + q].prev_node = -1;
         ctx->nodes[trellis_node + q].quant     = q;
     }
@@ -549,12 +565,43 @@ static int find_slice_quant(AVCodecContext *avctx, const AVFrame *pic,
         slice_bits[q]  = bits;
         slice_score[q] = error;
     }
+    if (slice_bits[max_quant] <= ctx->bits_per_mb * mbs_per_slice) {
+        slice_bits[max_quant + 1]  = slice_bits[max_quant];
+        slice_score[max_quant + 1] = slice_score[max_quant] + 1;
+        overquant = max_quant;
+    } else {
+        for (q = max_quant + 1; q < 128; q++) {
+            bits  = 0;
+            error = 0;
+            if (q < MAX_STORED_Q) {
+                qmat = ctx->quants[q];
+            } else {
+                qmat = ctx->custom_q;
+                for (i = 0; i < 64; i++)
+                    qmat[i] = ctx->profile_info->quant[i] * q;
+            }
+            for (i = 0; i < ctx->num_planes; i++) {
+                bits += estimate_slice_plane(ctx, &error, i,
+                                             src, pic->linesize[i],
+                                             mbs_per_slice,
+                                             num_cblocks[i], plane_factor[i],
+                                             qmat);
+            }
+            if (bits <= ctx->bits_per_mb * mbs_per_slice)
+                break;
+        }
+
+        slice_bits[max_quant + 1]  = bits;
+        slice_score[max_quant + 1] = error;
+        overquant = q;
+    }
+    ctx->nodes[trellis_node + max_quant + 1].quant = overquant;
 
     bits_limit = mbs * ctx->bits_per_mb;
-    for (pq = min_quant; pq <= max_quant; pq++) {
+    for (pq = min_quant; pq < max_quant + 2; pq++) {
         prev = trellis_node - TRELLIS_WIDTH + pq;
 
-        for (q = min_quant; q <= max_quant; q++) {
+        for (q = min_quant; q < max_quant + 2; q++) {
             cur = trellis_node + q;
 
             bits  = ctx->nodes[prev].bits + slice_bits[q];
@@ -578,7 +625,7 @@ static int find_slice_quant(AVCodecContext *avctx, const AVFrame *pic,
 
     error = ctx->nodes[trellis_node + min_quant].score;
     pq    = trellis_node + min_quant;
-    for (q = min_quant + 1; q <= max_quant; q++) {
+    for (q = min_quant + 1; q < max_quant + 2; q++) {
         if (ctx->nodes[trellis_node + q].score <= error) {
             error = ctx->nodes[trellis_node + q].score;
             pq    = trellis_node + q;
@@ -606,8 +653,7 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
     avctx->coded_frame->pict_type = AV_PICTURE_TYPE_I;
     avctx->coded_frame->key_frame = 1;
 
-    pkt_size = ctx->mb_width * ctx->mb_height * 64 * 3 * 12
+    pkt_size = ctx->frame_size + FF_MIN_BUFFER_SIZE;
-               + ctx->num_slices * 2 + 200 + FF_MIN_BUFFER_SIZE;
 
     if ((ret = ff_alloc_packet(pkt, pkt_size)) < 0) {
         av_log(avctx, AV_LOG_ERROR, "Error getting output packet.\n");
@@ -762,9 +808,13 @@ static av_cold int encode_init(AVCodecContext *avctx)
             break;
     ctx->bits_per_mb   = ctx->profile_info->br_tab[i];
 
+    ctx->frame_size = ctx->num_slices * (2 + 2 * ctx->num_planes
+                                         + (2 * mps * ctx->bits_per_mb) / 8)
+                      + 200;
+
     min_quant = ctx->profile_info->min_quant;
     max_quant = ctx->profile_info->max_quant;
-    for (i = min_quant; i <= max_quant; i++) {
+    for (i = min_quant; i < MAX_STORED_Q; i++) {
         for (j = 0; j < 64; j++)
             ctx->quants[i][j] = ctx->profile_info->quant[j] * i;
     }
@@ -773,6 +823,8 @@ static av_cold int encode_init(AVCodecContext *avctx)
 
     av_log(avctx, AV_LOG_DEBUG, "profile %d, %d slices, %d bits per MB\n",
            ctx->profile, ctx->num_slices, ctx->bits_per_mb);
+    av_log(avctx, AV_LOG_DEBUG, "estimated frame size %d\n",
+           ctx->frame_size);
 
     ctx->nodes = av_malloc((ctx->slices_width + 1) * TRELLIS_WIDTH
                            * sizeof(*ctx->nodes));
@@ -780,7 +832,7 @@ static av_cold int encode_init(AVCodecContext *avctx)
         encode_close(avctx);
         return AVERROR(ENOMEM);
     }
-    for (i = min_quant; i <= max_quant; i++) {
+    for (i = min_quant; i < max_quant + 2; i++) {
         ctx->nodes[i].prev_node = -1;
         ctx->nodes[i].bits      = 0;
         ctx->nodes[i].score     = 0;