vpxenc: add quantizer histogram display

Add the --q-hist=n option, which displays a histogram with n buckets for
the quantizer selected on each frame.

Change-Id: I59b020c26b0acae0b938685081d9932bd98df5c9

vpxenc.c

@@ -23,6 +23,7 @@
 #include <stdarg.h>
 #include <string.h>
 #include <limits.h>
+#include <assert.h>
 #include "vpx/vpx_encoder.h"
 #if USE_POSIX_MMAP
 #include <sys/types.h>
@@ -909,12 +910,14 @@ static const arg_def_t framerate        = ARG_DEF(NULL, "fps", 1,
         "Stream frame rate (rate/scale)");
 static const arg_def_t use_ivf          = ARG_DEF(NULL, "ivf", 0,
         "Output IVF (default is WebM)");
+static const arg_def_t q_hist_n         = ARG_DEF(NULL, "q-hist", 1,
+        "Show quantizer histogram (n-buckets)");
 static const arg_def_t *main_args[] =
 {
     &debugmode,
     &outputfile, &codecarg, &passes, &pass_arg, &fpf_name, &limit, &deadline,
     &best_dl, &good_dl, &rt_dl,
-    &verbosearg, &psnrarg, &use_ivf,
+    &verbosearg, &psnrarg, &use_ivf, &q_hist_n,
     NULL
 };
 
@@ -1107,6 +1110,149 @@ static void usage_exit()
     exit(EXIT_FAILURE);
 }
 
+
+#define HIST_BAR_MAX 40
+struct hist_bucket
+{
+    int low, high, count;
+};
+
+
+static int merge_hist_buckets(struct hist_bucket *bucket,
+                              int *buckets_,
+                              int max_buckets)
+{
+    int small_bucket = 0, merge_bucket = INT_MAX, big_bucket=0;
+    int buckets = *buckets_;
+    int i;
+
+    /* Find the extrema for this list of buckets */
+    big_bucket = small_bucket = 0;
+    for(i=0; i < buckets; i++)
+    {
+        if(bucket[i].count < bucket[small_bucket].count)
+            small_bucket = i;
+        if(bucket[i].count > bucket[big_bucket].count)
+            big_bucket = i;
+    }
+
+    /* If we have too many buckets, merge the smallest with an ajacent
+     * bucket.
+     */
+    while(buckets > max_buckets)
+    {
+        int last_bucket = buckets - 1;
+
+        // merge the small bucket with an adjacent one.
+        if(small_bucket == 0)
+            merge_bucket = 1;
+        else if(small_bucket == last_bucket)
+            merge_bucket = last_bucket - 1;
+        else if(bucket[small_bucket - 1].count < bucket[small_bucket + 1].count)
+            merge_bucket = small_bucket - 1;
+        else
+            merge_bucket = small_bucket + 1;
+
+        assert(abs(merge_bucket - small_bucket) <= 1);
+        assert(small_bucket < buckets);
+        assert(big_bucket < buckets);
+        assert(merge_bucket < buckets);
+
+        if(merge_bucket < small_bucket)
+        {
+            bucket[merge_bucket].high = bucket[small_bucket].high;
+            bucket[merge_bucket].count += bucket[small_bucket].count;
+        }
+        else
+        {
+            bucket[small_bucket].high = bucket[merge_bucket].high;
+            bucket[small_bucket].count += bucket[merge_bucket].count;
+            merge_bucket = small_bucket;
+        }
+
+        assert(bucket[merge_bucket].low != bucket[merge_bucket].high);
+
+        buckets--;
+
+        /* Remove the merge_bucket from the list, and find the new small
+         * and big buckets while we're at it
+         */
+        big_bucket = small_bucket = 0;
+        for(i=0; i < buckets; i++)
+        {
+            if(i > merge_bucket)
+                bucket[i] = bucket[i+1];
+
+            if(bucket[i].count < bucket[small_bucket].count)
+                small_bucket = i;
+            if(bucket[i].count > bucket[big_bucket].count)
+                big_bucket = i;
+        }
+
+    }
+
+    *buckets_ = buckets;
+    return bucket[big_bucket].count;
+}
+
+
+static void show_histogram(const struct hist_bucket *bucket,
+                           int                       buckets,
+                           int                       total,
+                           int                       scale)
+{
+    int i;
+
+    for(i=0; i<buckets; i++)
+    {
+        int len;
+        int j;
+        float pct;
+
+        pct = 100.0 * (float)bucket[i].count / (float)total;
+        len = HIST_BAR_MAX * bucket[i].count / scale;
+        if(len < 1)
+            len = 1;
+        assert(len <= HIST_BAR_MAX);
+
+        if(bucket[i].low == bucket[i].high)
+            fprintf(stderr, "%4d   : ", bucket[i].low);
+        else
+            fprintf(stderr, "%4d-%2d: ", bucket[i].low, bucket[i].high);
+
+        for(j=0; j<HIST_BAR_MAX; j++)
+            fprintf(stderr, j<len?"=":" ");
+        fprintf(stderr, "\t%5d (%6.2f%%)\n",bucket[i].count,pct);
+    }
+}
+
+
+static void show_q_histogram(const int counts[64], int max_buckets)
+{
+    struct hist_bucket bucket[64];
+    int buckets = 0;
+    int total = 0;
+    int scale;
+    int i;
+
+
+    for(i=0; i<64; i++)
+    {
+        if(counts[i])
+        {
+            bucket[buckets].low = bucket[buckets].high = i;
+            bucket[buckets].count = counts[i];
+            buckets++;
+            total += counts[i];
+        }
+    }
+
+    fprintf(stderr, "Quantizer Selection:\n");
+    scale = merge_hist_buckets(bucket, &buckets, max_buckets);
+    show_histogram(bucket, buckets, total, scale);
+}
+
+
 #define ARG_CTRL_CNT_MAX 10
 
 int main(int argc, const char **argv_)
@@ -1145,6 +1291,8 @@ int main(int argc, const char **argv_)
     double                   psnr_totals[4] = {0, 0, 0, 0};
     int                      psnr_count = 0;
     stereo_format_t          stereo_fmt = STEREO_FORMAT_MONO;
+    int                      counts[64]={0};
+    int                      show_q_hist_buckets=0;
 
     exec_name = argv_[0];
     ebml.last_pts_ms = -1;
@@ -1228,6 +1376,8 @@ int main(int argc, const char **argv_)
             out_fn = arg.val;
         else if (arg_match(&arg, &debugmode, argi))
             ebml.debug = 1;
+        else if (arg_match(&arg, &q_hist_n, argi))
+            show_q_hist_buckets = arg_parse_uint(&arg);
         else
             argj++;
     }
@@ -1648,6 +1798,16 @@ int main(int argc, const char **argv_)
             vpx_usec_timer_mark(&timer);
             cx_time += vpx_usec_timer_elapsed(&timer);
             ctx_exit_on_error(&encoder, "Failed to encode frame");
+
+            if(cfg.g_pass != VPX_RC_FIRST_PASS)
+            {
+                int q;
+
+                vpx_codec_control(&encoder, VP8E_GET_LAST_QUANTIZER_64, &q);
+                ctx_exit_on_error(&encoder, "Failed to read quantizer");
+                counts[q]++;
+            }
+
             got_data = 0;
 
             while ((pkt = vpx_codec_get_cx_data(&encoder, &iter)))
@@ -1758,6 +1918,9 @@ int main(int argc, const char **argv_)
             break;
     }
 
+    if (show_q_hist_buckets)
+        show_q_histogram(counts, show_q_hist_buckets);
+
     vpx_img_free(&raw);
     free(argv);
     return EXIT_SUCCESS;