[FFmpeg-devel] [PATCH v3 1/9] lavc/libopenh264enc: Add default qmin/qmax support

[Linjie Fu]

Set default QP range to (1, 51) instead of (2, 32).

QP = 0 is not well supported currently in libopenh264. If iMaxQp/iMinQp
equals 0, the QP range would be changed unexpectedly inside libopenh264
with a warning:

Warning:Change QP Range from(0,51) to (12,42)

[1] <https://github.com/cisco/openh264/blob/master/codec/encoder/core/src/encoder_ext.cpp#L375>
[2] <https://github.com/cisco/openh264/issues/3259>

Signed-off-by: Linjie Fu <linjie.fu at intel.com>
---
 libavcodec/libopenh264enc.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/libavcodec/libopenh264enc.c b/libavcodec/libopenh264enc.c
index dd5d4ee..c7ae5b1 100644
--- a/libavcodec/libopenh264enc.c
+++ b/libavcodec/libopenh264enc.c
@@ -135,6 +135,9 @@ FF_ENABLE_DEPRECATION_WARNINGS
     param.iTargetBitrate             = avctx->bit_rate;
     param.iMaxBitrate                = FFMAX(avctx->rc_max_rate, avctx->bit_rate);
     param.iRCMode                    = RC_QUALITY_MODE;
+    // QP = 0 is not well supported, so default to (1, 51)
+    param.iMaxQp                     = avctx->qmax >= 0 ? av_clip(avctx->qmax, 1, 51) : 51;
+    param.iMinQp                     = avctx->qmin >= 0 ? av_clip(avctx->qmin, 1, param.iMaxQp) : 1;
     param.iTemporalLayerNum          = 1;
     param.iSpatialLayerNum           = 1;
     param.bEnableDenoise             = 0;
@@ -331,6 +334,12 @@ static int svc_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
     return 0;
 }
 
+static const AVCodecDefault svc_enc_defaults[] = {
+    { "qmin",      "-1"    },
+    { "qmax",      "-1"    },
+    { NULL },
+};
+
 AVCodec ff_libopenh264_encoder = {
     .name           = "libopenh264",
     .long_name      = NULL_IF_CONFIG_SMALL("OpenH264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10"),
@@ -344,6 +353,7 @@ AVCodec ff_libopenh264_encoder = {
     .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
     .pix_fmts       = (const enum AVPixelFormat[]){ AV_PIX_FMT_YUV420P,
                                                     AV_PIX_FMT_NONE },
+    .defaults       = svc_enc_defaults,
     .priv_class     = &class,
     .wrapper_name   = "libopenh264",
 };
-- 
2.7.4