[FFmpeg-devel] [PATCH] rtpenc_vp8: Use 15-bit PictureIDs

From: kevin@muxable.com
To: ffmpeg-devel@ffmpeg.org
Cc: martin@martin.st, Kevin Wang <kevmo314@gmail.com>,
	Kevin Wang <kevin@muxable.com>
Subject: [FFmpeg-devel] [PATCH] rtpenc_vp8: Use 15-bit PictureIDs
Date: Tue, 22 Mar 2022 14:25:11 -0400
Message-ID: <20220322182511.7747-1-kevin@muxable.com> (raw)

From: Kevin Wang <kevmo314@gmail.com>

7-bit PictureIDs are not supported by WebRTC:
https://groups.google.com/g/discuss-webrtc/c/333-L02vuWA

In practice, 15-bit PictureIDs offer better compatibility.

Signed-off-by: Kevin Wang <kevin@muxable.com>
---
 libavformat/rtpenc_vp8.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libavformat/rtpenc_vp8.c b/libavformat/rtpenc_vp8.c
index 671d245758..655d44517e 100644
--- a/libavformat/rtpenc_vp8.c
+++ b/libavformat/rtpenc_vp8.c
@@ -35,7 +35,8 @@ void ff_rtp_send_vp8(AVFormatContext *s1, const uint8_t *buf, int size)
     // partition id 0
     *s->buf_ptr++ = 0x90;
     *s->buf_ptr++ = 0x80; // Picture id present
-    *s->buf_ptr++ = s->frame_count++ & 0x7f;
+    *s->buf_ptr++ = ((s->frame_count & 0x7f00) >> 8) | 0x80;
+    *s->buf_ptr++ = s->frame_count++ & 0xff;
     // Calculate the number of remaining bytes
     header_size     = s->buf_ptr - s->buf;
     max_packet_size = s->max_payload_size - header_size;
-- 
2.34.1

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