avcodec.cpp

#include "avcodec.hpp"

#ifdef __cplusplus
extern "C" {
#endif

#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <libavutil/display.h>
#include <libavutil/imgutils.h>

#ifdef __cplusplus
}
#endif

extern AVInputFormat ff_mov_demuxer;
extern AVInputFormat ff_matroska_demuxer;
extern AVInputFormat ff_mp3_demuxer;
extern AVInputFormat ff_flac_demuxer;
extern AVInputFormat ff_wav_demuxer;
extern AVInputFormat ff_aac_demuxer;
extern AVInputFormat ff_ogg_demuxer;
extern AVCodec ff_h264_decoder;
extern AVCodec ff_hevc_decoder;
extern AVCodec ff_mpeg4_decoder;
extern AVCodec ff_vp9_decoder;
extern AVCodec ff_vp8_decoder;
extern AVCodec ff_mp3_decoder;
extern AVCodec ff_flac_decoder;
extern AVCodec ff_aac_decoder;
extern AVCodec ff_vorbis_decoder;

void avcodec_init()
{
    av_log_set_level(AV_LOG_ERROR);
}

struct avcodec_decoder_struct {
    const cv::Mat* mat;
    ptrdiff_t read_index;
    AVFormatContext* container;
    AVCodecContext* codec;
    AVIOContext* avio;
    int video_stream_index;
};

static int avcodec_decoder_read_callback(void* d_void, uint8_t* buf, int buf_size)
{
    avcodec_decoder d = static_cast<avcodec_decoder>(d_void);
    size_t buf_len = d->mat->total() - d->read_index;
    size_t read_len = (buf_len > buf_size) ? buf_size : buf_len;
    if (read_len == 0) {
        return AVERROR_EOF;
    }
    memmove(buf, d->mat->data + d->read_index, read_len);
    d->read_index += read_len;
    return read_len;
}

static int64_t avcodec_decoder_seek_callback(void* d_void, int64_t offset, int whence)
{
    avcodec_decoder d = static_cast<avcodec_decoder>(d_void);
    uint8_t* to;
    switch (whence) {
    case SEEK_SET:
        to = d->mat->data + offset;
        break;
    case SEEK_CUR:
        to = d->mat->data + d->read_index + offset;
        break;
    case SEEK_END:
        to = d->mat->data + d->mat->total() + offset;
        break;
    case AVSEEK_SIZE:
        return d->mat->total();
    default:
        return -1;
    }
    if (to < d->mat->data) {
        return -1;
    }
    if (to >= (d->mat->data + d->mat->total())) {
        return -1;
    }
    d->read_index = (to - d->mat->data);
    return 0;
}

static bool avcodec_decoder_is_audio(const avcodec_decoder d)
{
    if (!d->container) {
        return false;
    }
    if (d->container->iformat == &ff_mp3_demuxer) {
        return true;
    }
    if (d->container->iformat == &ff_flac_demuxer) {
        return true;
    }
    if (d->container->iformat == &ff_wav_demuxer) {
        return true;
    }
    if (d->container->iformat == &ff_aac_demuxer) {
        return true;
    }
    if (d->container->iformat == &ff_ogg_demuxer) {
        return true;
    }
    return false;
}

bool avcodec_decoder_is_streamable(const opencv_mat mat) {
    const int64_t probeBytesLimit = 32 * 1024; // Define the probe limit
    const size_t atomHeaderSize = 8;
    int64_t bytesRead = 0;
    const cv::Mat* buf = static_cast<const cv::Mat*>(mat);
    size_t bufSize = buf->total();
    size_t peekSize = MIN(bufSize, probeBytesLimit);

    while(bytesRead + atomHeaderSize <= peekSize) {
        // Read atom size and type
        uint32_t atomSize = (buf->data[bytesRead] << 24) | (buf->data[bytesRead + 1] << 16) |
                            (buf->data[bytesRead + 2] << 8) | buf->data[bytesRead + 3];

        // Validate atom size
        if (atomSize < atomHeaderSize || atomSize + bytesRead > bufSize) {
            break;
        }

        // Read atom type
        char atomType[4];
        memcpy(atomType, &buf->data[bytesRead + 4], 4);

        // Check for 'moov' and 'mdat' atoms using byte comparison
        if (memcmp(atomType, "moov", 4) == 0) {
            return true;
        }
        if (memcmp(atomType, "mdat", 4) == 0) {
            return false;
        }

        // Move to the next atom position
        bytesRead += atomSize; // Atom size includes the header size
    }

    return false;
}

avcodec_decoder avcodec_decoder_create(const opencv_mat buf, const bool hevc_enabled)
{
    avcodec_decoder d = new struct avcodec_decoder_struct();
    memset(d, 0, sizeof(struct avcodec_decoder_struct));
    d->mat = static_cast<const cv::Mat*>(buf);

    d->container = avformat_alloc_context();
    if (!d->container) {
        avcodec_decoder_release(d);
        return NULL;
    }

    d->avio = avio_alloc_context(
      NULL, 0, 0, d, avcodec_decoder_read_callback, NULL, avcodec_decoder_seek_callback);
    if (!d->avio) {
        avcodec_decoder_release(d);
        return NULL;
    }
    d->container->pb = d->avio;

    int res = avformat_open_input(&d->container, NULL, NULL, NULL);
    if (res < 0) {
        avformat_free_context(d->container);
        d->container = NULL;
        avcodec_decoder_release(d);
        return NULL;
    }

    // perform a quick search for the video stream index in the container
    AVCodecParameters* codec_params = NULL;
    for (int i = 0; i < d->container->nb_streams; i++) {
        if (d->container->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            codec_params = d->container->streams[i]->codecpar;
            d->video_stream_index = i;
            break;
        }
    }

    // call avformat_find_stream_info only if no header was found (i.e. mpeg-ts),
    // or if the duration, width, or height are unknown.
    // this is an expensive operation that could involve frame decoding, perform judiciously.
    bool isAudioOnly = avcodec_decoder_is_audio(d);
    if ((!isAudioOnly && (!codec_params || codec_params->width <= 0 || codec_params->height <= 0)) ||
        d->container->duration <= 0) {
        res = avformat_find_stream_info(d->container, NULL);
        if (res < 0) {
            avcodec_decoder_release(d);
            return NULL;
        }

        if (isAudioOnly) {
            // in this case, quit out fast since we won't be decoding this anyway
            // (audio is metadata-only)
            return d;
        }

        // repeat the search for the video stream index
        if (!codec_params) {
            for (int i = 0; i < d->container->nb_streams; i++) {
                if (d->container->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
                    codec_params = d->container->streams[i]->codecpar;
                    d->video_stream_index = i;
                    break;
                }
            }
            if (!codec_params) {
                avcodec_decoder_release(d);
                return NULL;
            }
        }
    }

    const AVCodec* codec = avcodec_find_decoder(codec_params->codec_id);
    if (!codec) {
        avcodec_decoder_release(d);
        return NULL;
    }

    if (codec->id == AV_CODEC_ID_HEVC && !hevc_enabled) {
        avcodec_decoder_release(d);
        return NULL;
    }

    d->codec = avcodec_alloc_context3(codec);

    res = avcodec_parameters_to_context(d->codec, codec_params);
    if (res < 0) {
        avcodec_decoder_release(d);
        return NULL;
    }

    res = avcodec_open2(d->codec, codec, NULL);
    if (res < 0) {
        avcodec_decoder_release(d);
        return NULL;
    }

    return d;
}

int avcodec_decoder_get_width(const avcodec_decoder d)
{
    if (d->codec) {
        return d->codec->width;
    }
    return 0;
}

int avcodec_decoder_get_height(const avcodec_decoder d)
{
    if (d->codec) {
        return d->codec->height;
    }
    return 0;
}

int avcodec_decoder_get_orientation(const avcodec_decoder d)
{
    if (!d->container) {
        return CV_IMAGE_ORIENTATION_TL;
    }
    if (!d->codec) {
        return CV_IMAGE_ORIENTATION_TL;
    }
    CVImageOrientation orientation = CV_IMAGE_ORIENTATION_TL;
    AVDictionaryEntry* tag =
      av_dict_get(d->container->streams[d->video_stream_index]->metadata, "rotate", NULL, 0);
    int rotation = 0;
    if (tag) {
        rotation = atoi(tag->value);
    } else {
        const uint8_t* side_data =
          av_stream_get_side_data(d->container->streams[d->video_stream_index], AV_PKT_DATA_DISPLAYMATRIX, NULL);
        if (side_data) {
            rotation = (360 - (int)(av_display_rotation_get((const int32_t*)side_data))) % 360;
        }
    }
    switch (rotation) {
    case 90:
        orientation = CV_IMAGE_ORIENTATION_RT;
        break;
    case 180:
        orientation = CV_IMAGE_ORIENTATION_BR;
        break;
    case 270:
        orientation = CV_IMAGE_ORIENTATION_LB;
        break;
    }
    return orientation;
}

float avcodec_decoder_get_duration(const avcodec_decoder d)
{
    if (d->container) {
        return d->container->duration / (float)(AV_TIME_BASE);
    }
    return 0;
}

const char* avcodec_decoder_get_description(const avcodec_decoder d)
{
    if (d->container) {
        if (d->container->iformat == &ff_mov_demuxer) {
            return "MOV";
        }
        if (d->container->iformat == &ff_matroska_demuxer) {
            return "WEBM";
        }
        if (d->container->iformat == &ff_mp3_demuxer) {
            return "MP3";
        }
        if (d->container->iformat == &ff_flac_demuxer) {
            return "FLAC";
        }
        if (d->container->iformat == &ff_wav_demuxer) {
            return "WAV";
        }
        if (d->container->iformat == &ff_aac_demuxer) {
            return "AAC";
        }
        if (d->container->iformat == &ff_ogg_demuxer) {
            return "OGG";
        }
    }
    return "";
}

bool avcodec_decoder_has_subtitles(const avcodec_decoder d) {
    for (unsigned int i = 0; i < d->container->nb_streams; i++) {
        AVStream* stream = d->container->streams[i];
        if (stream->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE) {
            return true;
        }
    }
    return false;
}

static int avcodec_decoder_copy_frame(const avcodec_decoder d, opencv_mat mat, AVFrame* frame) {
    auto cvMat = static_cast<cv::Mat*>(mat);

    int res = avcodec_receive_frame(d->codec, frame);
    if (res >= 0) {
        // Calculate the step size based on the cv::Mat's width
        int stepSize = 4 * cvMat->cols; // Assuming the cv::Mat is in BGRA format, which has 4 channels
        if (cvMat->cols % 32 != 0) {
            int width = cvMat->cols + 32 - (cvMat->cols % 32);
            stepSize = 4 * width;
        }
        if (!opencv_mat_set_row_stride(mat, stepSize)) {
            return -1;
        }

        // Create SwsContext for converting the frame format and scaling
        struct SwsContext* sws = sws_getContext(
            frame->width, frame->height, (AVPixelFormat)(frame->format), // Source dimensions and format
            cvMat->cols, cvMat->rows, AV_PIX_FMT_BGRA, // Destination dimensions and format
            SWS_BILINEAR, // Specify the scaling algorithm; you can choose another according to your needs
            NULL, NULL, NULL);

        // The linesizes and data pointers for the destination
        int dstLinesizes[4];
        av_image_fill_linesizes(dstLinesizes, AV_PIX_FMT_BGRA, stepSize / 4);
        uint8_t* dstData[4] = {cvMat->data, NULL, NULL, NULL};

        // Perform the scaling and format conversion
        sws_scale(sws, frame->data, frame->linesize, 0, frame->height, dstData, dstLinesizes);

        // Free the SwsContext
        sws_freeContext(sws);
    }

    return res;
}

static int avcodec_decoder_decode_packet(const avcodec_decoder d, opencv_mat mat, AVPacket* packet)
{
    int res = avcodec_send_packet(d->codec, packet);
    if (res < 0) {
        return res;
    }

    AVFrame* frame = av_frame_alloc();
    if (!frame) {
        return -1;
    }

    res = avcodec_decoder_copy_frame(d, mat, frame);
    av_frame_free(&frame);

    return res;
}

bool avcodec_decoder_decode(const avcodec_decoder d, opencv_mat mat)
{
    if (!d) {
        return false;
    }
    if (!d->container) {
        return false;
    }
    if (!d->codec) {
        return false;
    }
    AVPacket packet;
    bool done = false;
    bool success = false;
    while (!done) {
        int res = av_read_frame(d->container, &packet);
        if (res < 0) {
            return false;
        }
        if (packet.stream_index == d->video_stream_index) {
            res = avcodec_decoder_decode_packet(d, mat, &packet);
            if (res >= 0) {
                success = true;
                done = true;
            }
            else if (res != AVERROR(EAGAIN)) {
                done = true;
            }
        }
        av_packet_unref(&packet);
    }
    return success;
}

void avcodec_decoder_release(avcodec_decoder d)
{
    if (d->codec) {
        avcodec_free_context(&d->codec);
    }

    if (d->container) {
        avformat_close_input(&d->container);
    }

    if (d->avio) {
        avio_flush(d->avio);
        av_free(d->avio->buffer);
        av_free(d->avio);
    }

    delete d;
}