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c++encodingmp4openh264

Muxing h264 into mp4 using libmp4v2 and OpenH264

Iam using OpenH264 as encoder and I want to mux its output into a playable mp4 using libmp4v2

The resulting .mp4 only work partially. It is playable in VLC and MPC-HC but not in Windows Media Player nor the Windows 10 "Movie and Tv" App.
My goal is it that the file works with all these players.

Both Windows players are telling my they don't know the codec so they can't play it back: enter image description here
This is not really true since I can play a manually muxed file using the same h264 bitstream by using FFmpeg from the cli:

ffmpeg -i "testenc.h264" -c:v copy -f mp4 "output.mp4"

According to this knowlege I think my encoding process works fine and the problem is located in the muxing procedure.

Edit: Thanks to Rudolfs Bundulis answer who pointed out that the SPS/PPS data is missing I was able to restructure my code. It now trys to include the missing data by analysing the encoders bitstream and calling MP4AddH264SequenceParameterSet or MP4AddH264PictureParameterSet when necessary. But still without success.

My full code: 

#include "stdafx.h"
#include <iostream>
#include <stdio.h>
#include <chrono>
#include "mp4v2/mp4v2.h"
#include "codec_api.h"

#define WIDTH 1280
#define HEIGHT 960
#define DURATION MP4_INVALID_DURATION
#define NAL_SPS 1
#define NAL_PPS 2
#define NAL_I 3
#define NAL_P 4

using namespace std;
using namespace chrono;

/* Just some dummy data to see artifacts ect */
void prepareFrame(int i, SSourcePicture* pic) {
    for (int y = 0; y<HEIGHT; y++) {
        for (int x = 0; x<WIDTH; x++) {
            pic->pData[0][y * WIDTH + x] = x + y + i * 3;
        }
    }

    for (int y = 0; y<HEIGHT / 2; y++) {
        for (int x = 0; x<WIDTH / 2; x++) {
            pic->pData[1][y * (WIDTH / 2) + x] = 128 + y + i * 2;
            pic->pData[2][y * (WIDTH / 2) + x] = 64 + x + i * 5;
        }
    }
    pic->uiTimeStamp = (i + 1) * 1000 / 75;
}

void printHex(const unsigned char* arr, int len) {
    for (int i = 0; i < len; i++) {
        if (arr[i] < 16) {
            cout << "0";
        }
        cout << hex << (int)arr[i] << " ";
    }
    cout << endl;
}

void mp4Encode(MP4FileHandle mp4Handle, MP4TrackId track, uint8_t * bitstream, int length) {

    int index = -1;

    if (bitstream[0] == 0 && bitstream[1] == 0 && bitstream[2] == 0 && bitstream[3] == 1 && bitstream[4] == 0x67) {
        index = NAL_SPS;
    }
    if (bitstream[0] == 0 && bitstream[1] == 0 && bitstream[2] == 0 && bitstream[3] == 1 && bitstream[4] == 0x68) {
        index = NAL_PPS;
    }
    if (bitstream[0] == 0 && bitstream[1] == 0 && bitstream[2] == 0 && bitstream[3] == 1 && bitstream[4] == 0x65) {
        index = NAL_I;
    }
    if (bitstream[0] == 0 && bitstream[1] == 0 && bitstream[2] == 0 && bitstream[3] == 1 && bitstream[4] == 0x61) {
        index = NAL_P;
    }

    switch (index) {
    case NAL_SPS:
        cout << "Detected SPS" << endl;
        MP4AddH264SequenceParameterSet(mp4Handle, track, bitstream + 4, length - 4);
        break;
    case NAL_PPS:
        cout << "Detected PPS" << endl;
        MP4AddH264PictureParameterSet(mp4Handle, track, bitstream + 4, length - 4);
        break;
    case NAL_I:
    {
        cout << "Detected I" << endl;
        uint8_t * IFrameData = (uint8_t *) malloc(length + 1);
        IFrameData[0] = (length - 3) >> 24;
        IFrameData[1] = (length - 3) >> 16;
        IFrameData[2] = (length - 3) >> 8;
        IFrameData[3] = (length - 3) & 0xff;

        memcpy(IFrameData + 4, bitstream + 3, length - 3);

        if (!MP4WriteSample(mp4Handle, track, IFrameData, length + 1, DURATION, 0, 1)) {
            cout << "Error when writing sample" << endl;
            system("pause");
            exit(1);
        }
        free(IFrameData);

        break;
    }
    case NAL_P:
    {
        cout << "Detected P" << endl;
        bitstream[0] = (length - 4) >> 24;
        bitstream[1] = (length - 4) >> 16;
        bitstream[2] = (length - 4) >> 8;
        bitstream[3] = (length - 4) & 0xff;

        if (!MP4WriteSample(mp4Handle, track, bitstream, length, DURATION, 0, 1)) {
            cout << "Error when writing sample" << endl;
            system("pause");
            exit(1);
        }
        break;
    }
    }
    if (index == -1) {
        cout << "Could not detect nal type" << endl;
        system("pause");
        exit(1);
    }
}

int main()
{
    //just to measure performance
    high_resolution_clock::time_point time = high_resolution_clock::now(); 

    //Create MP4
    MP4FileHandle mp4Handle = MP4Create("test.mp4", 0);
    MP4SetTimeScale(mp4Handle, 90000);

    //Create filestream for binary h264 output for testing 
    FILE* targetFile;
    targetFile = fopen("testenc.h264", "wb");

    if (!targetFile) {
        cout << "failed to create file" << endl;
        system("pause");
        return 1;
    }

    ISVCEncoder *encoder;
    int rv = WelsCreateSVCEncoder(&encoder);

    //Encoder params
    SEncParamExt param;
    encoder->GetDefaultParams(&param);
    param.iUsageType = CAMERA_VIDEO_REAL_TIME;
    param.fMaxFrameRate = 75.f;
    param.iLtrMarkPeriod = 75;
    param.iPicWidth = WIDTH;
    param.iPicHeight = HEIGHT;
    param.iTargetBitrate = 40000000;
    param.bEnableDenoise = false;
    param.iSpatialLayerNum = 1;
    param.bUseLoadBalancing = false;
    param.bEnableSceneChangeDetect = false;
    param.bEnableBackgroundDetection = false;
    param.bEnableAdaptiveQuant = false;
    param.bEnableFrameSkip = false; 
    param.iMultipleThreadIdc = 16;
    //param.uiIntraPeriod = 10;

    for (int i = 0; i < param.iSpatialLayerNum; i++) {
        param.sSpatialLayers[i].iVideoWidth = WIDTH >> (param.iSpatialLayerNum - 1 - i);
        param.sSpatialLayers[i].iVideoHeight = HEIGHT >> (param.iSpatialLayerNum - 1 - i);
        param.sSpatialLayers[i].fFrameRate = 75.f;
        param.sSpatialLayers[i].iSpatialBitrate = param.iTargetBitrate;
        param.sSpatialLayers[i].uiProfileIdc = PRO_BASELINE;
        param.sSpatialLayers[i].uiLevelIdc = LEVEL_4_2;
        param.sSpatialLayers[i].iDLayerQp = 42;

        SSliceArgument sliceArg;
        sliceArg.uiSliceMode = SM_FIXEDSLCNUM_SLICE;
        sliceArg.uiSliceNum = 16;

        param.sSpatialLayers[i].sSliceArgument = sliceArg;      
    }

    param.uiMaxNalSize = 1500;
    param.iTargetBitrate *= param.iSpatialLayerNum;
    encoder->InitializeExt(&param);
    int videoFormat = videoFormatI420;
    encoder->SetOption(ENCODER_OPTION_DATAFORMAT, &videoFormat);

    MP4TrackId track = MP4AddH264VideoTrack(mp4Handle, 90000, 90000/25, WIDTH, HEIGHT, 66, 192, 42, 3);
    MP4SetVideoProfileLevel(mp4Handle, 0x7f);

    SFrameBSInfo info;
    memset(&info, 0, sizeof(SFrameBSInfo));
    SSourcePicture pic;
    memset(&pic, 0, sizeof(SSourcePicture));
    pic.iPicWidth = WIDTH;
    pic.iPicHeight = HEIGHT;
    pic.iColorFormat = videoFormatI420;
    pic.iStride[0] = pic.iPicWidth;
    pic.iStride[1] = pic.iStride[2] = pic.iPicWidth >> 1;
    int frameSize = WIDTH * HEIGHT * 3 / 2;
    pic.pData[0] = new unsigned char[frameSize];
    pic.pData[1] = pic.pData[0] + WIDTH * HEIGHT;
    pic.pData[2] = pic.pData[1] + (WIDTH * HEIGHT >> 2);
    for (int num = 0; num<75; num++) {
        cout << "-------FRAME " << dec << num << "-------" << endl;
        prepareFrame(num, &pic);
        rv = encoder->EncodeFrame(&pic, &info);
        if (!rv == cmResultSuccess) {
            cout << "encode failed" << endl;
            continue;
        }
        if (info.eFrameType != videoFrameTypeSkip) {

            for (int i = 0; i < info.iLayerNum; ++i) {
                int len = 0;
                const SLayerBSInfo& layerInfo = info.sLayerInfo[i];
                for (int j = 0; j < layerInfo.iNalCount; ++j) {
                    cout << "Layer: " << dec << i << "| Nal: " << j << endl << "Hex: ";
                    printHex(info.sLayerInfo[i].pBsBuf + len, 20);
                    mp4Encode(mp4Handle, track, info.sLayerInfo[i].pBsBuf + len, layerInfo.pNalLengthInByte[j]);
                    len += layerInfo.pNalLengthInByte[j];
                }
                //mp4Encode(mp4Handle, track, info.sLayerInfo[i].pBsBuf, len);
            }
            //fwrite(info.sLayerInfo[0].pBsBuf, 1, len, targetFile);

        }
    }
    int res = 0;
    encoder->GetOption(ENCODER_OPTION_PROFILE, &res);
    cout << res << endl;
    fflush(targetFile);
    fclose(targetFile);

    encoder->Uninitialize();
    WelsDestroySVCEncoder(encoder);
    //Close MP4
    MP4Close(mp4Handle);

    cout << "done in: ";
    cout << duration_cast<milliseconds>(high_resolution_clock::now() - time).count() << endl;
    system("pause");
    return 0;
}
Solution

  • You can use MP4Box from GPAC to analyze the MP4 box layouts of both files. enter image description here As seen here, the bad file is missing the SPS/PPS data in the avcC box. The same NAL units are most likely stored in the NAL units as well, but the specification requires them to be also present in the avcC box (some players handle SPS/PPS inlined in the stream but that is a bad practice since it breaks seeking and what not since you don't know which sample groups reference which parameter sets upfront).

    A quick google search for libmp4v2 gave me this example which shows how to actually call MP4AddH264SequenceParameterSet/MP4AddH264PictureParameterSet to provide the SPS/PPS, while you only call MP4WriteSample which could be the issue.

    My subjective opinion - I have never used libmp4v2 but if you don't know how to use it too just use ffmpeg instead - more examples and the community will be bigger. Muxing H.264 into mp4 is quite simple, again lots of examples on the internet.

    SUMMARY

    1. MP4 requires the SPS/PPS information to be in the avcC box - some players may be able to decode the stream if these units are put inline with the samples, but to conform to the specification, one should always have the avcC box present, otherwise a player is free to fail to play the stream.
    2. Depending on the library used, there may be different techniques how to signal the SPS/PPS to the muxer, but as seen here with libmp4v2, one must use P4AddH264SequenceParameterSet/MP4AddH264PictureParameterSet. To obtain the SPS/PPS data one should parse the bitstream. This varies depending on the bitstream format (if annex b format with start codes or avcc format with interleaved lengths are used - see this for more info). When the SPS/PPS info is extracted it should be passed to the muxing library.
    3. Handle SPS/PPS change with care. The specification actually states that you can have multiple stsd stream description boxes and then reference them, but as far as I recall, Windows Media Player handles this poorly, so if possible stick to a single SPS/PPS set. One should be able to configure the encoder not to emit duplicate SPS/PPS entries on each keyframe.