avcodec/libvpxenc: add a way to explicitly set temporal layer id

In order for rate control to correctly allocate bitrate to each temporal
layer, correct temporal layer id has to be set to each frame. This
commit provides the ability to set correct temporal layer id for each
frame.
Signed-off-by: James Zern <jzern@google.com>

doc/encoders.texi

@@ -1918,7 +1918,17 @@ Currently supports the following options.
 @table @option
 @item 0
 No temporal layering flags are provided internally,
-relies on flags being passed in using metadata in AVFrame.
+relies on flags being passed in using @code{metadata} field in @code{AVFrame}
+with following keys.
+@table @option
+@item vp8-flags
+Sets the flags passed into the encoder to indicate the referencing scheme for
+the current frame.
+Refer to function @code{vpx_codec_encode} in @code{vpx/vpx_encoder.h} for more
+details.
+@item temporal_id
+Explicitly sets the temporal id of the current frame to encode.
+@end table
 @item 2
 Two temporal layers. 0-1...
 @item 3

libavcodec/libvpxenc.c

@@ -1519,11 +1519,22 @@ static int vpx_encode(AVCodecContext *avctx, AVPacket *pkt,
 #endif
         if (frame->pict_type == AV_PICTURE_TYPE_I)
             flags |= VPX_EFLAG_FORCE_KF;
-        if (CONFIG_LIBVPX_VP8_ENCODER && avctx->codec_id == AV_CODEC_ID_VP8 && frame->metadata) {
+        if (frame->metadata) {
             AVDictionaryEntry* en = av_dict_get(frame->metadata, "vp8-flags", NULL, 0);
             if (en) {
                 flags |= strtoul(en->value, NULL, 10);
             }
+
+            memset(&layer_id, 0, sizeof(layer_id));
+
+            en = av_dict_get(frame->metadata, "temporal_id", NULL, 0);
+            if (en) {
+                layer_id.temporal_layer_id = strtoul(en->value, NULL, 10);
+#ifdef VPX_CTRL_VP9E_SET_MAX_INTER_BITRATE_PCT
+                layer_id.temporal_layer_id_per_spatial[0] = layer_id.temporal_layer_id;
+#endif
+                layer_id_valid = 1;
+            }
         }
 
         if (sd) {

libavcodec/version.h

@@ -29,7 +29,7 @@
 
 #define LIBAVCODEC_VERSION_MAJOR  58
 #define LIBAVCODEC_VERSION_MINOR  68
-#define LIBAVCODEC_VERSION_MICRO 101
+#define LIBAVCODEC_VERSION_MICRO 102
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \