[FFmpeg-devel] [PATCH v5 2/5] lavc/libopenh264enc: add default gop size and bit rate

[Martin Storsjö]

On Tue, 28 Apr 2020, Linjie Fu wrote:

> It would be 200kbps bitrate with gop size = 12 by default
> which generated too many IDR frames in rather low bit rate.
> The quality would be poor.
>
> Set these default values to -1 to check whether it's specified
> by user explicitly.
>
> Use 2Mbps bitrate as nvenc sugguested, and leave gop size
> untouched in libopenh264.
>
> Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> ---
> libavcodec/libopenh264enc.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/libavcodec/libopenh264enc.c b/libavcodec/libopenh264enc.c
> index 1b6b53a..0951412 100644
> --- a/libavcodec/libopenh264enc.c
> +++ b/libavcodec/libopenh264enc.c
> @@ -37,6 +37,8 @@
> #define SM_SIZELIMITED_SLICE SM_DYN_SLICE
> #endif
> 
> +#define TARGET_BITRATE_DEFAULT 2*1000*1000
> +
> typedef struct SVCContext {
>     const AVClass *av_class;
>     ISVCEncoder *encoder;
> @@ -132,7 +134,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
>     param.fMaxFrameRate              = 1/av_q2d(avctx->time_base);
>     param.iPicWidth                  = avctx->width;
>     param.iPicHeight                 = avctx->height;
> -    param.iTargetBitrate             = avctx->bit_rate;
> +    param.iTargetBitrate             = avctx->bit_rate > 0 ? avctx->bit_rate : TARGET_BITRATE_DEFAULT;
>     param.iMaxBitrate                = FFMAX(avctx->rc_max_rate, avctx->bit_rate);
>     param.iRCMode                    = RC_QUALITY_MODE;
>     // QP = 0 is not well supported, so clip to (1, 51)
> @@ -148,7 +150,8 @@ FF_ENABLE_DEPRECATION_WARNINGS
>     param.bEnableFrameSkip           = s->skip_frames;
>     param.bEnableLongTermReference   = 0;
>     param.iLtrMarkPeriod             = 30;
> -    param.uiIntraPeriod              = avctx->gop_size;
> +    if (avctx->gop_size)
> +        param.uiIntraPeriod          = avctx->gop_size;

This should be gop_size > 0, or maybe >= 0. Otherwise we'll end up setting 
the default -1.

// Martin