[FFmpeg-cvslog] avcodec/libaomenc: Add parameter for avif single image encoding

[Vignesh Venkatasubramanian]

ffmpeg | branch: master | Vignesh Venkatasubramanian <vigneshv-at-google.com at ffmpeg.org> | Mon May  2 14:37:01 2022 -0700| [ab05e9a7f277b3eb47b23d2b0a1a90d972b404bd] | committer: Gyan Doshi

avcodec/libaomenc: Add parameter for avif single image encoding

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 <vigneshv at google.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ab05e9a7f277b3eb47b23d2b0a1a90d972b404bd
---

 libavcodec/libaomenc.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/libavcodec/libaomenc.c b/libavcodec/libaomenc.c
index 054903e6e2..0411773bbf 100644
--- a/libavcodec/libaomenc.c
+++ b/libavcodec/libaomenc.c
@@ -100,6 +100,7 @@ typedef struct AOMEncoderContext {
     int enable_restoration;
     int usage;
     int tune;
+    int still_picture;
     int enable_rect_partitions;
     int enable_1to4_partitions;
     int enable_ab_partitions;
@@ -747,6 +748,18 @@ static av_cold int aom_init(AVCodecContext *avctx,
     if (res < 0)
         return res;
 
+    if (ctx->still_picture) {
+        // 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;
+        // 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) {
@@ -1291,6 +1304,7 @@ 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
+    { "still-picture", "Encode in single frame mode (typically used for still AVIF images).", OFFSET(still_picture), AV_OPT_TYPE_BOOL, {.i64 = 0}, -1, 1, VE },
     { "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},