[Libav-user] Problem Encoding H264 Video

[Alex Cohn]

On Jul 23, 2013 11:54 AM, "Marika Marszalkowski" <marikaner at gmail.com>
wrote:
>
> I should have added that oformat->video_codec is AV_CODEC_ID_H264, of
course.
>
> Best,
> Marika
>
>
> On Mon, Jul 22, 2013 at 8:00 PM, Marika Marszalkowski <marikaner at gmail.com>
wrote:
>>
>> Hello everyone,
>>
>> I have been trying to create an encoded h264 Video from multiple images
(QImage), but I can't really achieve this.
>>
>> This list is my last resort and I totally hope there is someone out
there who can help me with this not as complicated problem. I am not sure
what the exact problem is - the video is created, but it is kind of jumpy,
so that an image is shown and it stays there for two second and then there
is a very short sequence (like half a second) and it's not moving again.
Also the first 40 encoded frames, return 0 (SUCCESS) but got_packet_ptr is
0.
>>
>> So this is how I create the video with its header:
>>
>>         AVCodec *codec = avcodec_find_encoder(oformat->video_codec);
>>
>>
>>         m_codecContext = avcodec_alloc_context3(codec);
>>
>>         m_codecContext->gop_size = 30;
>>
>>         m_codecContext->sample_fmt = AV_SAMPLE_FMT_NONE;
>>
>>         m_codecContext->bit_rate = width * height;
>>
>>         m_codecContext->width = width;
>>
>>         m_codecContext->height = height;
>>
>>         m_codecContext->time_base = (AVRational){1,frameRate};
>>
>>         m_codecContext->pix_fmt = AV_PIX_FMT_YUV420P;
>>
>>
>>         formatCtx = avformat_alloc_context();
>>
>>         if(!formatCtx)
>>
>>         {
>>
>>            printf("Error allocating format context\n");
>>
>>         }
>>
>>         formatCtx->oformat = oformat;
>>
>>         formatCtx->video_codec_id = oformat->video_codec;
>>
>>         snprintf(formatCtx->filename, sizeof(formatCtx->filename), "%s",
outputFileName.toStdString().c_str());
>>
>>
>>         AVStream *videoStream = av_new_stream(formatCtx, 0);
>>
>>         if(!videoStream)
>>
>>         {
>>
>>            printf("Could not allocate stream\n");
>>
>>         }
>>
>>         videoStream->codec = m_codecContext;
>>
>>
>>         if(formatCtx->oformat->flags & AVFMT_GLOBALHEADER)
>>
>>         {
>>
>>            m_codecContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
>>
>>         }
>>
>>
>>         avcodec_open2(m_codecContext, codec, NULL);
>>
>>         avio_open(&formatCtx->pb, outputFileName.toStdString().c_str(),
AVIO_FLAG_WRITE);
>>
>>         avformat_write_header(formatCtx, NULL);
>>
>>
>>
>> and this is how I add the frames:
>>
>>
>>
>>
>>         AVFrame *frame = avcodec_alloc_frame();
>>
>>         int size = m_codecContext->width * m_codecContext->height;
>>
>>         int numBytes = avpicture_get_size(m_codecContext->pix_fmt,
m_codecContext->width, m_codecContext->height);
>>
>>
>>         QSharedPointer<BlendImage> img = imageData;
>>
>>
>>         uint8_t *outbuf = (uint8_t *)malloc(numBytes);
>>
>>         uint8_t *picture_buf = (uint8_t *)av_malloc(numBytes);
>>
>>
>>         if (true)
>>
>>         {
>>
>>             int ret = av_image_fill_arrays(frame->data, frame->linesize,
picture_buf, m_codecContext->pix_fmt, m_codecContext->width,
m_codecContext->height, 1);
>>
>>
>>             frame->data[0] = picture_buf;
>>
>>             frame->data[1] = frame->data[0] + size;
>>
>>             frame->data[2] = frame->data[1] + size/4;
>>
>>             frame->linesize[0] = m_codecContext->width;
>>
>>             frame->linesize[1] = m_codecContext->width/2;
>>
>>             frame->linesize[2] = m_codecContext->width/2;
>>
>>
>>             fflush(stdout);
>>
>>             for (int y = 0; y < m_codecContext->height; y++)
>>
>>             {
>>
>>                 for (int x = 0; x < m_codecContext->width; x++)
>>
>>                 {
>>
>>                     unsigned char b = img->bits()[(y *
m_codecContext->width + x) * 4 + 0];
>>
>>                     unsigned char g = img->bits()[(y *
m_codecContext->width + x) * 4 + 1];
>>
>>                     unsigned char r = img->bits()[(y *
m_codecContext->width + x) * 4 + 2];
>>
>>
>>                     unsigned char Y = (0.257 * r) + (0.504 * g) + (0.098
* b) + 16;
>>
>>
>>                     frame->data[0][y * frame->linesize[0] + x] = Y;
>>
>>
>>                     if (y % 2 == 0 && x % 2 == 0)
>>
>>                     {
>>
>>                         unsigned char V = (0.439 * r) - (0.368 * g) -
(0.071 * b) + 128;
>>
>>                         unsigned char U = -(0.148 * r) - (0.291 * g) +
(0.439 * b) + 128;
>>
>>
>>                         frame->data[1][y/2 * frame->linesize[1] + x/2] =
U;
>>
>>                         frame->data[2][y/2 * frame->linesize[2] + x/2] =
V;
>>
>>                     }
>>
>>                }
>>
>>             }
>>
>>             int pts = (1.0 / 30.0) * 9000.0 * frameIndex;
>>
>>             frame->pts = pts;
>>
>>
>>             int got_packet_ptr;
>>
>>
>>             AVPacket packet;
>>
>>             av_init_packet(&packet);
>>
>>             packet.data = outbuf;
>>
>>             packet.size = numBytes;
>>
>>             packet.stream_index = formatCtx->streams[0]->index;
>>
>>             packet.flags |= AV_PKT_FLAG_KEY;
>>
>>             packet.pts = packet.dts = pts;
>>
>>
>>             m_codecContext->coded_frame->pts = pts;
>>
>>
>>             ret = avcodec_encode_video2(m_codecContext, &packet, frame,
&got_packet_ptr);
>>
>>
>>
>>             if (got_packet_ptr != 0)
>>
>>             {
>>
>>                 m_codecContext->coded_frame->pts = pts;
>>
>>
>>                 if (m_codecContext->coded_frame->pts !=
(0x8000000000000000LL))
>>
>>                     pts = av_rescale_q(m_codecContext->coded_frame->pts,
m_codecContext->time_base, formatCtx->streams[0]->time_base);
>>
>>
>>                    packet.pts = pts;
>>
>>
>>                 if(m_codecContext->coded_frame->key_frame)
>>
>>                 {
>>
>>                    packet.flags |= AV_PKT_FLAG_KEY;
>>
>>                 }
>>
>>
>>
>>                 std::cout << "pts: " << packet.pts << ", dts: "  <<
packet.dts << std::endl;
>>
>>
>>                 av_interleaved_write_frame(formatCtx, &packet);
>>
>>                 av_free_packet(&packet);
>>
>>             }
>>
>>         }
>>
>>
>>         free(picture_buf);
>>
>>         free(outbuf);
>>
>>         av_free(frame);
>>
>>
>>
>> and of course in the end:
>>
>>
>>         av_write_trailer(formatCtx);
>>
>>         fclose(m_file);
>>
>>         avcodec_close(m_codecContext);
>>
>>         av_free(m_codecContext);
>>
>>
>>
>> I think this has something to do with the PTS/DTS values. PTS values
start at 120 (as the first 40 frames are omitted) and are increased by 3
((1.0 / 30.0) * 9000.0 * frameIndex) and the DTS values start at -6 also
being increased by 3 per frame. But it might also be the settings or
anything else. I feel like I have tried everything I was able to find on
the internet and it's still wrong. I am desperate, help would be soooo
appreciated!
>>
>>
>> Cheers,
>>
>> Marika

What is your output format?
Alex
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