prores: allow user to set fixed quantiser

libavcodec/proresenc.c

@@ -184,6 +184,7 @@ typedef struct ProresContext {
     int num_slices;
     int num_planes;
     int bits_per_mb;
+    int force_quant;
 
     char *vendor;
     int quant_sel;
@@ -397,7 +398,9 @@ static int encode_slice(AVCodecContext *avctx, const AVFrame *pic,
     int plane_factor, is_chroma;
     uint16_t *qmat;
 
-    if (quant < MAX_STORED_Q) {
+    if (ctx->force_quant) {
+        qmat = ctx->quants[0];
+    } else if (quant < MAX_STORED_Q) {
         qmat = ctx->quants[quant];
     } else {
         qmat = ctx->custom_q;
@@ -750,6 +753,7 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
     // slices
     for (y = 0; y < ctx->mb_height; y++) {
         mbs_per_slice = ctx->mbs_per_slice;
+        if (!ctx->force_quant) {
             for (x = mb = 0; x < ctx->mb_width; x += mbs_per_slice, mb++) {
                 while (ctx->mb_width - x < mbs_per_slice)
                     mbs_per_slice >>= 1;
@@ -761,10 +765,11 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
                 ctx->slice_q[x] = ctx->nodes[q].quant;
                 q = ctx->nodes[q].prev_node;
             }
+        }
 
         mbs_per_slice = ctx->mbs_per_slice;
         for (x = mb = 0; x < ctx->mb_width; x += mbs_per_slice, mb++) {
-            q = ctx->slice_q[mb];
+            q = ctx->force_quant ? ctx->force_quant : ctx->slice_q[mb];
 
             while (ctx->mb_width - x < mbs_per_slice)
                 mbs_per_slice >>= 1;
@@ -859,6 +864,8 @@ static av_cold int encode_init(AVCodecContext *avctx)
         return AVERROR_INVALIDDATA;
     }
 
+    ctx->force_quant = avctx->global_quality / FF_QP2LAMBDA;
+    if (!ctx->force_quant) {
         if (!ctx->bits_per_mb) {
             for (i = 0; i < NUM_MB_LIMITS - 1; i++)
                 if (prores_mb_limits[i] >= ctx->mb_width * ctx->mb_height)
@@ -869,10 +876,6 @@ static av_cold int encode_init(AVCodecContext *avctx)
             return AVERROR_INVALIDDATA;
         }
 
-    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_STORED_Q; i++) {
@@ -880,13 +883,6 @@ static av_cold int encode_init(AVCodecContext *avctx)
                 ctx->quants[i][j] = ctx->quant_mat[j] * i;
         }
 
-    avctx->codec_tag   = ctx->profile_info->tag;
-
-    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));
         if (!ctx->nodes) {
@@ -904,6 +900,36 @@ static av_cold int encode_init(AVCodecContext *avctx)
             encode_close(avctx);
             return AVERROR(ENOMEM);
         }
+    } else {
+        int ls = 0;
+
+        if (ctx->force_quant > 64) {
+            av_log(avctx, AV_LOG_ERROR, "too large quantiser, maximum is 64\n");
+            return AVERROR_INVALIDDATA;
+        }
+
+        for (j = 0; j < 64; j++) {
+            ctx->quants[0][j] = ctx->quant_mat[j] * ctx->force_quant;
+            ls += av_log2((1 << 11)  / ctx->quants[0][j]) * 2 + 1;
+        }
+
+        ctx->bits_per_mb = ls * 8;
+        if (ctx->chroma_factor == CFACTOR_Y444)
+            ctx->bits_per_mb += ls * 4;
+        if (ctx->num_planes == 4)
+            ctx->bits_per_mb += ls * 4;
+    }
+
+    ctx->frame_size = ctx->num_slices * (2 + 2 * ctx->num_planes
+                                         + (2 * mps * ctx->bits_per_mb) / 8)
+                      + 200;
+
+    avctx->codec_tag   = ctx->profile_info->tag;
+
+    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);
 
     return 0;
 }