media/libstagefright/avc_utils.cpp

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "include/avc_utils.h"

#include <media/stagefright/foundation/ABitReader.h>
#include <media/stagefright/foundation/ADebug.h>
#include <media/stagefright/MediaDefs.h>
#include <media/stagefright/MediaErrors.h>
#include <media/stagefright/MetaData.h>

namespace android {

unsigned parseUE(ABitReader *br) {
    unsigned numZeroes = 0;
    while (br->getBits(1) == 0) {
        ++numZeroes;
    }

    unsigned x = br->getBits(numZeroes);

    return x + (1u << numZeroes) - 1;
}

// Determine video dimensions from the sequence parameterset.
void FindAVCDimensions(
        const sp<ABuffer> &seqParamSet, int32_t *width, int32_t *height) {
    ABitReader br(seqParamSet->data() + 1, seqParamSet->size() - 1);

    unsigned profile_idc = br.getBits(8);
    br.skipBits(16);
    parseUE(&br);  // seq_parameter_set_id

    unsigned chroma_format_idc = 1;  // 4:2:0 chroma format

    if (profile_idc == 100 || profile_idc == 110
            || profile_idc == 122 || profile_idc == 244
            || profile_idc == 44 || profile_idc == 83 || profile_idc == 86) {
        chroma_format_idc = parseUE(&br);
        if (chroma_format_idc == 3) {
            br.skipBits(1);  // residual_colour_transform_flag
        }
        parseUE(&br);  // bit_depth_luma_minus8
        parseUE(&br);  // bit_depth_chroma_minus8
        br.skipBits(1);  // qpprime_y_zero_transform_bypass_flag
        CHECK_EQ(br.getBits(1), 0u);  // seq_scaling_matrix_present_flag
    }

    parseUE(&br);  // log2_max_frame_num_minus4
    unsigned pic_order_cnt_type = parseUE(&br);

    if (pic_order_cnt_type == 0) {
        parseUE(&br);  // log2_max_pic_order_cnt_lsb_minus4
    } else if (pic_order_cnt_type == 1) {
        // offset_for_non_ref_pic, offset_for_top_to_bottom_field and
        // offset_for_ref_frame are technically se(v), but since we are
        // just skipping over them the midpoint does not matter.

        br.getBits(1);  // delta_pic_order_always_zero_flag
        parseUE(&br);  // offset_for_non_ref_pic
        parseUE(&br);  // offset_for_top_to_bottom_field

        unsigned num_ref_frames_in_pic_order_cnt_cycle = parseUE(&br);
        for (unsigned i = 0; i < num_ref_frames_in_pic_order_cnt_cycle; ++i) {
            parseUE(&br);  // offset_for_ref_frame
        }
    }

    parseUE(&br);  // num_ref_frames
    br.getBits(1);  // gaps_in_frame_num_value_allowed_flag

    unsigned pic_width_in_mbs_minus1 = parseUE(&br);
    unsigned pic_height_in_map_units_minus1 = parseUE(&br);
    unsigned frame_mbs_only_flag = br.getBits(1);

    *width = pic_width_in_mbs_minus1 * 16 + 16;

    *height = (2 - frame_mbs_only_flag)
        * (pic_height_in_map_units_minus1 * 16 + 16);

    if (!frame_mbs_only_flag) {
        br.getBits(1);  // mb_adaptive_frame_field_flag
    }

    br.getBits(1);  // direct_8x8_inference_flag

    if (br.getBits(1)) {  // frame_cropping_flag
        unsigned frame_crop_left_offset = parseUE(&br);
        unsigned frame_crop_right_offset = parseUE(&br);
        unsigned frame_crop_top_offset = parseUE(&br);
        unsigned frame_crop_bottom_offset = parseUE(&br);

        unsigned cropUnitX, cropUnitY;
        if (chroma_format_idc == 0  /* monochrome */) {
            cropUnitX = 1;
            cropUnitY = 2 - frame_mbs_only_flag;
        } else {
            unsigned subWidthC = (chroma_format_idc == 3) ? 1 : 2;
            unsigned subHeightC = (chroma_format_idc == 1) ? 2 : 1;

            cropUnitX = subWidthC;
            cropUnitY = subHeightC * (2 - frame_mbs_only_flag);
        }

        LOGV("frame_crop = (%u, %u, %u, %u), cropUnitX = %u, cropUnitY = %u",
             frame_crop_left_offset, frame_crop_right_offset,
             frame_crop_top_offset, frame_crop_bottom_offset,
             cropUnitX, cropUnitY);

        *width -=
            (frame_crop_left_offset + frame_crop_right_offset) * cropUnitX;
        *height -=
            (frame_crop_top_offset + frame_crop_bottom_offset) * cropUnitY;
    }
}

status_t getNextNALUnit(
        const uint8_t **_data, size_t *_size,
        const uint8_t **nalStart, size_t *nalSize,
        bool startCodeFollows) {
    const uint8_t *data = *_data;
    size_t size = *_size;

    *nalStart = NULL;
    *nalSize = 0;

    if (size == 0) {
        return -EAGAIN;
    }

    // Skip any number of leading 0x00.

    size_t offset = 0;
    while (offset < size && data[offset] == 0x00) {
        ++offset;
    }

    if (offset == size) {
        return -EAGAIN;
    }

    // A valid startcode consists of at least two 0x00 bytes followed by 0x01.

    if (offset < 2 || data[offset] != 0x01) {
        return ERROR_MALFORMED;
    }

    ++offset;

    size_t startOffset = offset;

    for (;;) {
        while (offset < size && data[offset] != 0x01) {
            ++offset;
        }

        if (offset == size) {
            if (startCodeFollows) {
                offset = size + 2;
                break;
            }

            return -EAGAIN;
        }

        if (data[offset - 1] == 0x00 && data[offset - 2] == 0x00) {
            break;
        }

        ++offset;
    }

    size_t endOffset = offset - 2;
    while (data[endOffset - 1] == 0x00) {
        --endOffset;
    }

    *nalStart = &data[startOffset];
    *nalSize = endOffset - startOffset;

    if (offset + 2 < size) {
        *_data = &data[offset - 2];
        *_size = size - offset + 2;
    } else {
        *_data = NULL;
        *_size = 0;
    }

    return OK;
}

static sp<ABuffer> FindNAL(
        const uint8_t *data, size_t size, unsigned nalType,
        size_t *stopOffset) {
    const uint8_t *nalStart;
    size_t nalSize;
    while (getNextNALUnit(&data, &size, &nalStart, &nalSize, true) == OK) {
        if ((nalStart[0] & 0x1f) == nalType) {
            sp<ABuffer> buffer = new ABuffer(nalSize);
            memcpy(buffer->data(), nalStart, nalSize);
            return buffer;
        }
    }

    return NULL;
}

sp<MetaData> MakeAVCCodecSpecificData(const sp<ABuffer> &accessUnit) {
    const uint8_t *data = accessUnit->data();
    size_t size = accessUnit->size();

    sp<ABuffer> seqParamSet = FindNAL(data, size, 7, NULL);
    if (seqParamSet == NULL) {
        return NULL;
    }

    int32_t width, height;
    FindAVCDimensions(seqParamSet, &width, &height);

    size_t stopOffset;
    sp<ABuffer> picParamSet = FindNAL(data, size, 8, &stopOffset);
    CHECK(picParamSet != NULL);

    size_t csdSize =
        1 + 3 + 1 + 1
        + 2 * 1 + seqParamSet->size()
        + 1 + 2 * 1 + picParamSet->size();

    sp<ABuffer> csd = new ABuffer(csdSize);
    uint8_t *out = csd->data();

    *out++ = 0x01;  // configurationVersion
    memcpy(out, seqParamSet->data() + 1, 3);  // profile/level...
    out += 3;
    *out++ = (0x3f << 2) | 1;  // lengthSize == 2 bytes
    *out++ = 0xe0 | 1;

    *out++ = seqParamSet->size() >> 8;
    *out++ = seqParamSet->size() & 0xff;
    memcpy(out, seqParamSet->data(), seqParamSet->size());
    out += seqParamSet->size();

    *out++ = 1;

    *out++ = picParamSet->size() >> 8;
    *out++ = picParamSet->size() & 0xff;
    memcpy(out, picParamSet->data(), picParamSet->size());

#if 0
    LOGI("AVC seq param set");
    hexdump(seqParamSet->data(), seqParamSet->size());
#endif

    sp<MetaData> meta = new MetaData;
    meta->setCString(kKeyMIMEType, MEDIA_MIMETYPE_VIDEO_AVC);

    meta->setData(kKeyAVCC, 0, csd->data(), csd->size());
    meta->setInt32(kKeyWidth, width);
    meta->setInt32(kKeyHeight, height);

    LOGI("found AVC codec config (%d x %d)", width, height);

    return meta;
}

bool IsIDR(const sp<ABuffer> &buffer) {
    const uint8_t *data = buffer->data();
    size_t size = buffer->size();

    bool foundIDR = false;

    const uint8_t *nalStart;
    size_t nalSize;
    while (getNextNALUnit(&data, &size, &nalStart, &nalSize, true) == OK) {
        CHECK_GT(nalSize, 0u);

        unsigned nalType = nalStart[0] & 0x1f;

        if (nalType == 5) {
            foundIDR = true;
            break;
        }
    }

    return foundIDR;
}

}  // namespace android