low_complexity_mode_encoder

/*
 * Copyright (c) 2026, Alliance for Open Media. All rights reserved.
 *
 * This source code is subject to the terms of the BSD 2 Clause License and
 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
 * was not distributed with this source code in the LICENSE file, you can
 * obtain it at www.aomedia.org/license/software. If the Alliance for Open
 * Media Patent License 1.0 was not distributed with this source code in the
 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
 */

// Low Complexity (LC) Mode Encoder
// ================================
//
// This is an example of a low complexity mode encoder. It takes an input
// file in Y4M format, passes it through the encoder with LC mode on, and
// writes the compressed frames to disk in IVF format.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "aom/aom_encoder.h"
#include "aom/aomcx.h"
#include "common/tools_common.h"
#include "common/video_writer.h"

static const char *exec_name;

void usage_exit(void) {
  fprintf(stderr,
          "Usage: %s <codec> <width> <height> <infile> <outfile> "
          "<keyframe-interval> <frames to encode>\n",
          exec_name);
  exit(EXIT_FAILURE);
}

static int encode_frame(aom_codec_ctx_t *codec, aom_image_t *img,
                        int frame_index, int flags, AvxVideoWriter *writer) {
  int got_pkts = 0;
  aom_codec_iter_t iter = NULL;
  const aom_codec_cx_pkt_t *pkt = NULL;
  const aom_codec_err_t res =
      aom_codec_encode(codec, img, frame_index, 1, flags);
  if (res != AOM_CODEC_OK) die_codec(codec, "Failed to encode frame");

  while ((pkt = aom_codec_get_cx_data(codec, &iter)) != NULL) {
    got_pkts = 1;

    if (pkt->kind == AOM_CODEC_CX_FRAME_PKT) {
      const int keyframe = (pkt->data.frame.flags & AOM_FRAME_IS_KEY) != 0;
      if (!aom_video_writer_write_frame(writer, pkt->data.frame.buf,
                                        pkt->data.frame.sz,
                                        pkt->data.frame.pts)) {
        die_codec(codec, "Failed to write compressed frame");
      }
      printf(keyframe ? "K" : ".");
      fflush(stdout);
    }
  }

  return got_pkts;
}

int main(int argc, char **argv) {
  FILE *infile = NULL;
  aom_codec_ctx_t codec;
  aom_codec_enc_cfg_t cfg;
  int frame_count = 0;
  aom_image_t raw;
  aom_codec_err_t res;
  AvxVideoInfo info;
  AvxVideoWriter *writer = NULL;
  const int fps = 30;
  const int bitrate = 400;
  int keyframe_interval = 0;
  int max_frames = 0;
  int frames_encoded = 0;
  const char *codec_arg = NULL;
  const char *width_arg = NULL;
  const char *height_arg = NULL;
  const char *infile_arg = NULL;
  const char *outfile_arg = NULL;
  const char *keyframe_interval_arg = NULL;
  const int usage = 0;  // AOM_USAGE_GOOD_QUALITY
  const int speed = 2;

  exec_name = argv[0];

  // Clear explicitly, as simply assigning "{ 0 }" generates
  // "missing-field-initializers" warning in some compilers.
  memset(&info, 0, sizeof(info));

  if (argc != 8) die("Invalid number of arguments");

  codec_arg = argv[1];
  width_arg = argv[2];
  height_arg = argv[3];
  infile_arg = argv[4];
  outfile_arg = argv[5];
  keyframe_interval_arg = argv[6];
  max_frames = (int)strtol(argv[7], NULL, 0);

  aom_codec_iface_t *encoder = get_aom_encoder_by_short_name(codec_arg);
  if (!encoder) die("Unsupported codec.");

  info.codec_fourcc = get_fourcc_by_aom_encoder(encoder);
  info.frame_width = (int)strtol(width_arg, NULL, 0);
  info.frame_height = (int)strtol(height_arg, NULL, 0);
  info.time_base.numerator = 1;
  info.time_base.denominator = fps;

  if (info.frame_width <= 0 || info.frame_height <= 0 ||
      (info.frame_width % 2) != 0 || (info.frame_height % 2) != 0) {
    die("Invalid frame size: %dx%d", info.frame_width, info.frame_height);
  }

  if (!aom_img_alloc(&raw, AOM_IMG_FMT_I420, info.frame_width,
                     info.frame_height, 1)) {
    die("Failed to allocate image.");
  }

  keyframe_interval = (int)strtol(keyframe_interval_arg, NULL, 0);
  if (keyframe_interval < 0) die("Invalid keyframe interval value.");

  printf("Using %s\n", aom_codec_iface_name(encoder));

  res = aom_codec_enc_config_default(encoder, &cfg, usage);
  if (res)
    die("Failed to get default codec config: %s", aom_codec_err_to_string(res));

  cfg.g_w = info.frame_width;
  cfg.g_h = info.frame_height;
  cfg.g_timebase.num = info.time_base.numerator;
  cfg.g_timebase.den = info.time_base.denominator;
  cfg.rc_target_bitrate = bitrate;
  cfg.g_lag_in_frames = 35;

  writer = aom_video_writer_open(outfile_arg, kContainerIVF, &info);
  if (!writer) die("Failed to open %s for writing.", outfile_arg);

  if (!(infile = fopen(infile_arg, "rb")))
    die("Failed to open %s for reading.", infile_arg);

  if (aom_codec_enc_init(&codec, encoder, &cfg, 0))
    die("Failed to initialize encoder");

  if (aom_codec_control(&codec, AOME_SET_CPUUSED, speed))
    die_codec(&codec, "Failed to set cpu-used");

  if (aom_codec_control(&codec, AV1E_SET_ENABLE_LOW_COMPLEXITY_DECODE, 1))
    die_codec(&codec, "Failed to set low-complexity mode");

  // Encode frames.
  while (aom_img_read(&raw, infile)) {
    int flags = 0;
    if (keyframe_interval > 0 && frame_count % keyframe_interval == 0)
      flags |= AOM_EFLAG_FORCE_KF;
    encode_frame(&codec, &raw, frame_count++, flags, writer);
    frames_encoded++;
    if (max_frames > 0 && frames_encoded >= max_frames) break;
  }

  // Flush encoder.
  while (encode_frame(&codec, NULL, -1, 0, writer)) continue;

  printf("\n");
  fclose(infile);
  printf("Processed %d frames.\n", frame_count);

  aom_img_free(&raw);
  if (aom_codec_destroy(&codec)) die_codec(&codec, "Failed to destroy codec.");

  aom_video_writer_close(writer);

  return EXIT_SUCCESS;
}