On Thu, Feb 17, 2022 at 1:00 PM James Almer <jamr...@gmail.com> wrote:
>
>
>
> On 2/17/2022 2:51 AM, Vignesh Venkatasubramanian wrote:
> > Add a parameter to libaom-av1 encoder to enforce some of the single
> > image constraints in the AV1 encoder. Setting this flag will limit
> > the encoder to producing exactly one frame and the sequence header
> > that is produced by the encoder will be conformant to the AVIF
> > specification [1].
> >
> > Part of Fixing Trac ticket #7621
> >
> > [1] https://aomediacodec.github.io/av1-avif
> >
> > Signed-off-by:: Vignesh Venkatasubramanian <vigne...@google.com>
> > ---
> > libavcodec/libaomenc.c | 14 ++++++++++++++
> > 1 file changed, 14 insertions(+)
> >
> > diff --git a/libavcodec/libaomenc.c b/libavcodec/libaomenc.c
> > index 963cc1bcbc..0398060a2f 100644
> > --- a/libavcodec/libaomenc.c
> > +++ b/libavcodec/libaomenc.c
> > @@ -99,6 +99,7 @@ typedef struct AOMEncoderContext {
> > int enable_restoration;
> > int usage;
> > int tune;
> > + int is_avif;
> > int enable_rect_partitions;
> > int enable_1to4_partitions;
> > int enable_ab_partitions;
> > @@ -746,6 +747,18 @@ static av_cold int aom_init(AVCodecContext *avctx,
> > if (res < 0)
> > return res;
> >
> > + if (ctx->is_avif) {
> > + // Set the maximum number of frames to 1. This will let libaom set
> > + // still_picture and reduced_still_picture_header to 1 in the
> > Sequence
> > + // Header as required by AVIF still images.
> > + enccfg.g_limit = 1;
>
> How will libaom react if you feed it more than 1 frame? Will it reject
> the input and return an error?
>
Yes, trying to encode a second frame after setting g_limit to 1 will
result in aom_codec_encode() returning an error.
> > + // Reduce memory usage for still images.
> > + enccfg.g_lag_in_frames = 0;
> > + // All frames will be key frames.
> > + enccfg.kf_max_dist = 0;
> > + enccfg.kf_mode = AOM_KF_DISABLED;
> > + }
> > +
> > /* Construct Encoder Context */
> > res = aom_codec_enc_init(&ctx->encoder, iface, &enccfg, flags);
> > if (res != AOM_CODEC_OK) {
> > @@ -1290,6 +1303,7 @@ static const AVOption options[] = {
> > { "psnr", NULL, 0, AV_OPT_TYPE_CONST, {.i64 =
> > AOM_TUNE_PSNR}, 0, 0, VE, "tune"},
> > { "ssim", NULL, 0, AV_OPT_TYPE_CONST, {.i64 =
> > AOM_TUNE_SSIM}, 0, 0, VE, "tune"},
> > FF_AV1_PROFILE_OPTS
> > + { "avif-image", "Encode in single frame mode for still AVIF images.",
> > OFFSET(is_avif), AV_OPT_TYPE_BOOL, {.i64 = -1}, -1, 1, VE },
>
> Judging by the above settings, this option should be called
> "still_picture". The description can mention it's required for AVIF output.
>
Renamed the variable and the option name to "still_picture".
> An alternative is to add new AVProfiles, giving them values outside the
> range that would be written into the sequence header. Like
> FF_PROFILE_AV1_MAIN_STILL_PICTURE with a value of 0x80,
> FF_PROFILE_AV1_HIGH_STILL_PICTURE with a value of 0x81, etc.
> Then you just look for avctx->profile & 0x80 to know it's a still picture.
>
> Of course considerations would need to be done to avoid problems, like
> the line "enccfg.g_profile = avctx->profile;" being changed to
> "enccfg.g_profile = avctx->profile & 0x3;" (We can define a constant for
> that 0x3 mask called profile_bits or whatever).
>
> > { "enable-rect-partitions", "Enable rectangular partitions",
> > OFFSET(enable_rect_partitions), AV_OPT_TYPE_BOOL, {.i64 = -1}, -1, 1, VE},
> > { "enable-1to4-partitions", "Enable 1:4/4:1 partitions",
> > OFFSET(enable_1to4_partitions), AV_OPT_TYPE_BOOL, {.i64 = -1}, -1, 1, VE},
> > { "enable-ab-partitions", "Enable ab shape partitions",
> > OFFSET(enable_ab_partitions), AV_OPT_TYPE_BOOL, {.i64 = -1}, -1, 1, VE},
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--
Vignesh
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