[FFmpeg-devel] [PATCH v2 1/2] avcodec/libopusenc: reload packet loss at encode

[Philip-Dylan Gleonec <philip-dylan.gleonec@savoirfairelinux.com>]

An estimation of packet loss is required by libopus to compute its FEC
data. Currently, this estimation is constant, and can not be changed
after configuration. This means an application using libopus through
ffmpeg can not adapt the packet loss estimation when the network
quality degrades.

This patch makes the encoder reload the packet_loss AVOption before
encoding samples, if fec is enabled and the packet loss estimation set
is different than the current one. This way an application can modify
the packet loss estimation by changing the AVOption. Typical use-case
is a RTP stream, where packet loss can be estimated from RTCP packets.

Signed-off-by: Philip-Dylan Gleonec <philip-dylan.gleonec@savoirfairelinux.com>
---
 libavcodec/libopusenc.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/libavcodec/libopusenc.c b/libavcodec/libopusenc.c
index c884075ffe..26d2082ffa 100644
--- a/libavcodec/libopusenc.c
+++ b/libavcodec/libopusenc.c
@@ -462,6 +462,23 @@ static int libopus_encode(AVCodecContext *avctx, AVPacket *avpkt,
     uint8_t *audio;
     int ret;
     int discard_padding;
+    int32_t opus_packet_loss = 0;
+
+    ret = opus_multistream_encoder_ctl(opus->enc,
+        OPUS_GET_PACKET_LOSS_PERC(&opus_packet_loss));
+    if (ret != OPUS_OK)
+        av_log(avctx, AV_LOG_WARNING,
+            "Unable to get expected packet loss percentage: %s\n",
+            opus_strerror(ret));
+
+    if (opus->opts.fec && (opus_packet_loss != opus->opts.packet_loss)) {
+        ret = opus_multistream_encoder_ctl(opus->enc,
+                                        OPUS_SET_PACKET_LOSS_PERC(opus->opts.packet_loss));
+        if (ret != OPUS_OK)
+            av_log(avctx, AV_LOG_WARNING,
+                "Unable to set expected packet loss percentage: %s\n",
+                opus_strerror(ret));
+    }
 
     if (frame) {
         ret = ff_af_queue_add(&opus->afq, frame);
-- 
2.25.1

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