media/encoder: use max bitrate if possible

define max bitrate for H264. Encoder could then use less bitrate
if he can.
It seems that it is not possible for VP8 et MPEG4

Issue: #80568
Change-Id: I8dc2cfc76ac02ef1f159a380a9e6ce31bc9eac06

src/media/media_encoder.cpp

@@ -84,7 +84,7 @@ void MediaEncoder::setOptions(const MediaDescription& args)
     codec_ = args.codec;
 
     av_dict_set(&options_, "payload_type", ring::to_string(args.payload_type).c_str(), 0);
-    av_dict_set(&options_, "bitrate", ring::to_string(args.codec->bitrate).c_str(), 0);
+    av_dict_set(&options_, "max_rate", ring::to_string(args.codec->bitrate).c_str(), 0);
 
     if (args.codec->systemCodecInfo.mediaType == MEDIA_AUDIO) {
         auto accountAudioCodec = std::static_pointer_cast<AccountAudioCodecInfo>(args.codec);
@@ -149,11 +149,16 @@ MediaEncoder::openOutput(const char *filename,
     }
 
     prepareEncoderContext(args.codec->systemCodecInfo.mediaType == MEDIA_VIDEO);
+    auto maxBitrate = 1000 * atoi(av_dict_get(options_, "max_rate", NULL, 0)->value);
+    RING_DBG("Using max bitrate %d", maxBitrate );
 
     /* let x264 preset override our encoder settings */
     if (args.codec->systemCodecInfo.avcodecId == AV_CODEC_ID_H264) {
         extractProfileLevelID(args.parameters, encoderCtx_);
         forcePresetX264();
+        // For H264 : define max bitrate in rc_max_rate
+        encoderCtx_->rc_max_rate = maxBitrate;
+
     } else if (args.codec->systemCodecInfo.avcodecId == AV_CODEC_ID_VP8) {
         // Using information given on this page:
         // http://www.webmproject.org/docs/encoder-parameters/
@@ -164,8 +169,11 @@ MediaEncoder::openOutput(const char *filename,
         encoderCtx_->qmin = 4;
         encoderCtx_->qmax = 56;
         encoderCtx_->gop_size = 999999;
+        // For VP8 : define max bitrate in bit_rate
+        encoderCtx_->bit_rate = maxBitrate;
     } else if (args.codec->systemCodecInfo.avcodecId == AV_CODEC_ID_MPEG4) {
-        encoderCtx_->rc_buffer_size = encoderCtx_->bit_rate;
+        // For MPEG4 : define max bitrate in bit_rate
+        encoderCtx_->bit_rate = maxBitrate;
     }
 
     int ret;
@@ -529,21 +537,12 @@ void MediaEncoder::prepareEncoderContext(bool is_video)
     if (encoderName == nullptr)
         encoderName = "encoder?";
 
-    // set some encoder settings here
-    encoderCtx_->bit_rate = 1000 * atoi(av_dict_get(options_, "bitrate",
-                                                    NULL, 0)->value);
-    RING_DBG("[%s] Using bitrate %d", encoderName, encoderCtx_->bit_rate);
-
-    // Use constant bitrate (video only)
-    if (is_video) {
-        RING_DBG("[%s] Using CBR", encoderName);
-        encoderCtx_->rc_min_rate = \
-            encoderCtx_->rc_max_rate = encoderCtx_->bit_rate;
-    }
 
     encoderCtx_->thread_count = std::thread::hardware_concurrency();
     RING_DBG("[%s] Using %d threads", encoderName, encoderCtx_->thread_count);
 
+    encoderCtx_->rc_buffer_size = encoderCtx_->rc_max_rate;
+
     if (is_video) {
         // resolution must be a multiple of two
         encoderCtx_->width = device_.width;