Use g_bit_depth during input validation

The libvpx encoder requires the input frames passed to it by the
application for encoding have the same bit-depth as codec bit-depth. If
the input bit-depth is less than codec bit-depth, then the application
must upshift the frame before passing it. The application may
communicate the actual input bit-depth via g_input_bit_depth so that
quality metrics are computed with reference to actual input.

As the input is expected to have same precision as codec bit-depth,
this commit modifies the input validator to use codec bit-depth.

Also updated API documentation to reflect these changes.

Change-Id: I9d2fe17b61f141f0ed47cf78f2e1f717a695541c

Author: ram-mohan

vp9/encoder/vp9_encoder.h

@@ -156,7 +156,7 @@ typedef struct VP9EncoderConfig {
   vpx_bit_depth_t bit_depth;     // Codec bit-depth.
   int width;                     // width of data passed to the compressor
   int height;                    // height of data passed to the compressor
-  unsigned int input_bit_depth;  // Input bit depth.
+  unsigned int input_bit_depth;  // Actual bit-depth of the input source
   double init_framerate;         // set to passed in framerate
   vpx_rational_t g_timebase;  // equivalent to g_timebase in vpx_codec_enc_cfg_t
   vpx_rational64_t g_timebase_in_ts;  // g_timebase * TICKS_PER_SEC

vp9/vp9_cx_iface.c

@@ -298,6 +298,8 @@ static vpx_codec_err_t validate_config(vpx_codec_alg_priv_t *ctx,
   RANGE_CHECK(extra_cfg, cq_level, 0, 63);
   RANGE_CHECK(cfg, g_bit_depth, VPX_BITS_8, VPX_BITS_12);
   RANGE_CHECK(cfg, g_input_bit_depth, 8, 12);
+  if (cfg->g_input_bit_depth > cfg->g_bit_depth)
+    ERROR("Input bit-depth must not exceed codec bit-depth");
   RANGE_CHECK(extra_cfg, content, VP9E_CONTENT_DEFAULT,
               VP9E_CONTENT_INVALID - 1);
 
@@ -369,9 +371,6 @@ static vpx_codec_err_t validate_config(vpx_codec_alg_priv_t *ctx,
       cfg->g_bit_depth > VPX_BITS_8) {
     ERROR("Codec high bit-depth not supported in profile < 2");
   }
-  if (cfg->g_profile <= (unsigned int)PROFILE_1 && cfg->g_input_bit_depth > 8) {
-    ERROR("Source high bit-depth not supported in profile < 2");
-  }
   if (cfg->g_profile > (unsigned int)PROFILE_1 &&
       cfg->g_bit_depth == VPX_BITS_8) {
     ERROR("Codec bit-depth 8 not supported in profile > 1");
@@ -458,7 +457,7 @@ static vpx_codec_err_t validate_img(vpx_codec_alg_priv_t *ctx,
       (img->fmt & VPX_IMG_FMT_HIGHBITDEPTH)) {
     const unsigned int h = img->d_h;
     const unsigned int w = img->d_w;
-    const unsigned int bit_depth = ctx->oxcf.input_bit_depth;
+    const unsigned int bit_depth = ctx->cfg.g_bit_depth;
     const int max_val = 1 << bit_depth;
     for (int plane = 0; plane < 3; ++plane) {
       const unsigned short *src = (const unsigned short *)img->planes[plane];

vpx/vpx_encoder.h

@@ -331,11 +331,15 @@ typedef struct vpx_codec_enc_cfg {
    */
   vpx_bit_depth_t g_bit_depth;
 
-  /*!\brief Bit-depth of the input frames
-   *
-   * This value identifies the bit_depth of the input frames in bits.
-   * Note that the frames passed as input to the encoder must have
-   * this bit-depth.
+  /*!\brief Bit-depth of the input source
+   *
+   * This value identifies the actual bit-depth of the input source in bits. It
+   * must not exceed codec bit-depth. Note that the frames passed as input to
+   * the encoder must match codec bit-depth. So, if there is a mismatch between
+   * source bit-depth and codec bit-depth, the application is required to
+   * upshift the frame to the codec bit-depth before passing it for encoding.
+   * This is only used for computing quality metrics relative to the actual
+   * input source and has no effect on the encoder's output.
    */
   unsigned int g_input_bit_depth;
 

vpxenc.c

@@ -497,7 +497,7 @@ static const arg_def_t bitdeptharg = ARG_DEF_ENUM(
     "Bit depth for codec (8 for version <=1, 10 or 12 for version 2)",
     bitdepth_enum);
 static const arg_def_t inbitdeptharg =
-    ARG_DEF(NULL, "input-bit-depth", 1, "Bit depth of input");
+    ARG_DEF(NULL, "input-bit-depth", 1, "Actual bit depth of input source");
 #endif
 
 static const struct arg_enum_list tune_content_enum[] = {