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Sur d’autres sites (5862)

  • Theora puts incorrect PTS presentation time on video with held frames

    17 mars 2012, par hexatron

    I have a problem with the packet PTS/DTS on OGG Theora videos with held frames.
    Theora tries to be clever about held frames by omitting duplicate frames
    and using the packet PTS/DTS (they are equal) to skip the held frame time.

    For example, a 2-second-long 10 fps video with frames
    
  A A A A A A A A A A B C D E F G G G G G
    
should encode with PTS (the frame start) as (note the encoder adds some dup frames)
    
    A 0.0
    
    A 0.1
    
    B 1.0
    
    C 1.1
    
    D 1.2
    
    E 1.3
    
    F 1.4
    
    G 1.5
    
    G 1.9
    
But libtheora (and ffmpeg) put an incorrect time stamp on frame B
    
(the first frame following a the dup frames)
    
    B 0.6
    
This causes video to hiccup on the mislabeled frame.
    

    
My crude fix for this is to use
    
    current frame PTS =  (next frame PTS time) - (one frame time)
    
and
    
    last frame PTS = duration - (one frame time)

    (I tried submitting a bug report for theora at xiph.org, as the theora site recommends, but could not figure out how to register for a login. I also noticed the reports were several years old, so decided to document this behavior here)

  • How to write NALs produced by x264_encoder_encode() using ffmpeg av_interleaved_write_frame()

    21 janvier 2013, par Haleeq Usman

    I have been trying to produce a "flv" video file in the following sequence :

    av_register_all();
    

    
// Open video file
    
if (avformat_open_input(&pFormatCtx, "6.mp4", NULL, NULL) != 0)
    
    return -1; // Couldn't open file
    

    
// Retrieve stream information
    
if (avformat_find_stream_info(pFormatCtx, NULL) < 0)
    
    return -1; // Couldn't find stream information
    

    
// Dump information about file onto standard error
    
av_dump_format(pFormatCtx, 0, "input_file.mp4", 0);
    

    
// Find the first video stream
    
videoStream = -1;
    
for (i = 0; i < pFormatCtx->nb_streams; i++)
    
    if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
    
        videoStream = i;
    
        break;
    
    }
    
if (videoStream == -1)
    
    return -1; // Didn't find a video stream
    

    
// Get a pointer to the codec context for the video stream
    
pCodecCtx = pFormatCtx->streams[videoStream]->codec;
    

    
// Find the decoder for the video stream
    
pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    
if (pCodec == NULL) {
    
    fprintf(stderr, "Unsupported codec!\n");
    
    return -1; // Codec not found
    
}
    
// Open codec
    
if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0)
    
    return -1; // Could not open codec
    

    
// Allocate video frame
    
pFrame = avcodec_alloc_frame();
    

    
// Allocate video frame
    
pFrame = avcodec_alloc_frame();
    

    
// Allocate an AVFrame structure
    
pFrameYUV420 = avcodec_alloc_frame();
    
if (pFrameYUV420 == NULL)
    
    return -1;
    

    
// Determine required buffer size and allocate buffer
    
numBytes = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
    
buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
    

    
// Assign appropriate parts of buffer to image planes in pFrameYUV420
    
// Note that pFrameYUV420 is an AVFrame, but AVFrame is a superset of AVPicture
    
avpicture_fill((AVPicture *) pFrameRGB, buffer, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
    

    
// Setup scaler
    
img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, SWS_BILINEAR, 0, 0, 0);
    
if (img_convert_ctx == NULL) {
    
    fprintf(stderr, "Cannot initialize the conversion context!\n");
    
    exit(1);
    
}
    

    
// Setup encoder/muxing now
    
filename = "output_file.flv";
    
fmt = av_guess_format("flv", filename, NULL);
    
if (fmt == NULL) {
    
    printf("Could not guess format.\n");
    
    return -1;
    
}
    
/* allocate the output media context */
    
oc = avformat_alloc_context();
    
if (oc == NULL) {
    
    printf("could not allocate context.\n");
    
    return -1;
    
}
    
oc->oformat = fmt;
    
snprintf(oc->filename, sizeof(oc->filename), "%s", filename);
    

    
video_st = NULL;
    
if (fmt->video_codec != AV_CODEC_ID_NONE) {
    
    video_st = add_stream(oc, &video_codec, fmt->video_codec);
    
}
    

    
// Let's see some information about our format
    
av_dump_format(oc, 0, filename, 1);
    

    
/* open the output file, if needed */
    
if (!(fmt->flags & AVFMT_NOFILE)) {
    
    ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);
    
    if (ret < 0) {
    
        fprintf(stderr, "Could not open '%s': %s\n", filename, av_err2str(ret));
    
        return 1;
    
    }
    
    }
    
/* Write the stream header, if any. */
    
ret = avformat_write_header(oc, NULL);
    
if (ret < 0) {
    
    fprintf(stderr, "Error occurred when opening output file: %s\n", av_err2str(ret));
    
    return 1;
    
}
    

    
// Setup x264 params
    
x264_param_t param;
    
x264_param_default_preset(&param, "veryfast", "zerolatency");
    
param.i_threads = 1;
    
param.i_width = video_st->codec->width;
    
param.i_height = video_st->codec->height;
    
param.i_fps_num = STREAM_FRAME_RATE; // 30 fps, same as video
    
param.i_fps_den = 1;
    
// Intra refres:
    
param.i_keyint_max = STREAM_FRAME_RATE;
    
param.b_intra_refresh = 1;
    
// Rate control:
    
param.rc.i_rc_method = X264_RC_CRF;
    
param.rc.f_rf_constant = 25;
    
param.rc.f_rf_constant_max = 35;
    
// For streaming:
    
param.b_repeat_headers = 1;
    
param.b_annexb = 1;
    
x264_param_apply_profile(&param, "baseline");
    

    
x264_t* encoder = x264_encoder_open(&param);
    
x264_picture_t pic_in, pic_out;
    
x264_picture_alloc(&pic_in, X264_CSP_I420, video_st->codec->width, video_st->codec->height);
    

    
x264_nal_t* nals;
    
int i_nals;
    

    
// The loop:
    
// 1. Read frames
    
// 2. Decode the frame
    
// 3. Attempt to re-encode using x264
    
// 4. Write the x264 encoded frame using av_interleaved_write_frame
    
while (av_read_frame(pFormatCtx, &packet) >= 0) {
    
    // Is this a packet from the video stream?
    
    if (packet.stream_index == videoStream) {
    
        // Decode video frame
    
        avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
    

    
        // Did we get a video frame?
    
        if (frameFinished) {
    
            sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pic_in.img.plane, pic_in.img.i_stride);
    
            int frame_size = x264_encoder_encode(encoder, &nals, &i_nals, &pic_in, &pic_out);
    

    
            if (frame_size >= 0) {
    
                if (i_nals < 0)
    
                    printf("invalid frame size: %d\n", i_nals);
    
                // write out NALs
    
                for (i = 0; i < i_nals; i++) {
    
                    // initalize a packet
    
                    AVPacket p;
    
                    av_init_packet(&p);
    
                    p.data = nals[i].p_payload;
    
                    p.size = nals[i].i_payload;
    
                    p.stream_index = video_st->index;
    
                    p.flags = AV_PKT_FLAG_KEY;
    
                    p.pts = AV_NOPTS_VALUE;
    
                    p.dts = AV_NOPTS_VALUE;
    
                    ret = av_interleaved_write_frame(oc, &p);
    
                }
    
            }
    
            printf("encoded frame #%d\n", frame_count);
    
            frame_count++;
    
        }
    
    }
    

    
    // Free the packet that was allocated by av_read_frame
    
    av_free_packet(&packet);
    
}
    

    
// Now we free up resources used/close codecs, and finally close our program.

    Here is the implementation for the add_stream() function :

    /* Add an output stream. */
    
static AVStream *add_stream(AVFormatContext *oc, AVCodec **codec, enum AVCodecID codec_id) {
    
    AVCodecContext *c;
    
    AVStream *st;
    
    int r;
    
    /* find the encoder */
    
    *codec = avcodec_find_encoder(codec_id);
    
    if (!(*codec)) {
    
        fprintf(stderr, "Could not find encoder for '%s'\n",
    
                avcodec_get_name(codec_id));
    
        exit(1);
    
    }
    
    st = avformat_new_stream(oc, *codec);
    
    if (!st) {
    
        fprintf(stderr, "Could not allocate stream\n");
    
        exit(1);
    
    }
    
    st->id = oc->nb_streams - 1;
    
    c = st->codec;
    
    switch ((*codec)->type) {
    
    case AVMEDIA_TYPE_AUDIO:
    
        st->id = 1;
    
        c->sample_fmt = AV_SAMPLE_FMT_FLTP;
    
        c->bit_rate = 64000;
    
        c->sample_rate = 44100;
    
        c->channels = 2;
    
        break;
    
    case AVMEDIA_TYPE_VIDEO:
    
        avcodec_get_context_defaults3(c, *codec);
    
        c->codec_id = codec_id;
    
        c->bit_rate = 500*1000;
    
        //c->rc_min_rate = 500*1000;
    
        //c->rc_max_rate = 500*1000;
    
        //c->rc_buffer_size = 500*1000;
    
        /* Resolution must be a multiple of two. */
    
        c->width = 1280;
    
        c->height = 720;
    
        /* timebase: This is the fundamental unit of time (in seconds) in terms
    
         * of which frame timestamps are represented. For fixed-fps content,
    
         * timebase should be 1/framerate and timestamp increments should be
    
         * identical to 1. */
    
        c->time_base.den = STREAM_FRAME_RATE;
    
        c->time_base.num = 1;
    
        c->gop_size = 12; /* emit one intra frame every twelve frames at most */
    
        c->pix_fmt = STREAM_PIX_FMT;
    
        if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
    
            /* just for testing, we also add B frames */
    
            c->max_b_frames = 2;
    
        }
    
        if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
    
            /* Needed to avoid using macroblocks in which some coeffs overflow.
    
             * This does not happen with normal video, it just happens here as
    
             * the motion of the chroma plane does not match the luma plane. */
    
            c->mb_decision = 2;
    
        }
    
        break;
    
    default:
    
        break;
    
    }
    
    /* Some formats want stream headers to be separate. */
    
    if (oc->oformat->flags & AVFMT_GLOBALHEADER)
    
        c->flags |= CODEC_FLAG_GLOBAL_HEADER;
    
    return st;
    
}

    After the encoding is complete, I check the output file output_file.flv. I notice it's size is very large : 101MB and it does not play. If I use ffmpeg to decode/encode the input file, then I get an output file about 83MB in size (which is about the same size as the original .mp4 file used as input). Also, the 83MB output from just using ffmpeg C api, as opposed to using x264 for the encoding step, plays just fine. Does anyone know where I am going wrong ? I have tried researching this for a few days now but with no luck :(. I feel that I am close to making it work, however, I just cannot figure out what I am doing wrong. Thank you !

  • How to write NALs produced by x264_encoder_encode() using ffmpeg av_interleaved_write_frame()

    21 janvier 2013, par Haleeq Usman

    I have been trying to produce a "flv" video file in the following sequence :

    av_register_all();
    

    
// Open video file
    
if (avformat_open_input(&pFormatCtx, "6.mp4", NULL, NULL) != 0)
    
    return -1; // Couldn't open file
    

    
// Retrieve stream information
    
if (avformat_find_stream_info(pFormatCtx, NULL) < 0)
    
    return -1; // Couldn't find stream information
    

    
// Dump information about file onto standard error
    
av_dump_format(pFormatCtx, 0, "input_file.mp4", 0);
    

    
// Find the first video stream
    
videoStream = -1;
    
for (i = 0; i < pFormatCtx->nb_streams; i++)
    
    if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
    
        videoStream = i;
    
        break;
    
    }
    
if (videoStream == -1)
    
    return -1; // Didn't find a video stream
    

    
// Get a pointer to the codec context for the video stream
    
pCodecCtx = pFormatCtx->streams[videoStream]->codec;
    

    
// Find the decoder for the video stream
    
pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    
if (pCodec == NULL) {
    
    fprintf(stderr, "Unsupported codec!\n");
    
    return -1; // Codec not found
    
}
    
// Open codec
    
if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0)
    
    return -1; // Could not open codec
    

    
// Allocate video frame
    
pFrame = avcodec_alloc_frame();
    

    
// Allocate video frame
    
pFrame = avcodec_alloc_frame();
    

    
// Allocate an AVFrame structure
    
pFrameYUV420 = avcodec_alloc_frame();
    
if (pFrameYUV420 == NULL)
    
    return -1;
    

    
// Determine required buffer size and allocate buffer
    
numBytes = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
    
buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
    

    
// Assign appropriate parts of buffer to image planes in pFrameYUV420
    
// Note that pFrameYUV420 is an AVFrame, but AVFrame is a superset of AVPicture
    
avpicture_fill((AVPicture *) pFrameRGB, buffer, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
    

    
// Setup scaler
    
img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, SWS_BILINEAR, 0, 0, 0);
    
if (img_convert_ctx == NULL) {
    
    fprintf(stderr, "Cannot initialize the conversion context!\n");
    
    exit(1);
    
}
    

    
// Setup encoder/muxing now
    
filename = "output_file.flv";
    
fmt = av_guess_format("flv", filename, NULL);
    
if (fmt == NULL) {
    
    printf("Could not guess format.\n");
    
    return -1;
    
}
    
/* allocate the output media context */
    
oc = avformat_alloc_context();
    
if (oc == NULL) {
    
    printf("could not allocate context.\n");
    
    return -1;
    
}
    
oc->oformat = fmt;
    
snprintf(oc->filename, sizeof(oc->filename), "%s", filename);
    

    
video_st = NULL;
    
if (fmt->video_codec != AV_CODEC_ID_NONE) {
    
    video_st = add_stream(oc, &video_codec, fmt->video_codec);
    
}
    

    
// Let's see some information about our format
    
av_dump_format(oc, 0, filename, 1);
    

    
/* open the output file, if needed */
    
if (!(fmt->flags & AVFMT_NOFILE)) {
    
    ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);
    
    if (ret < 0) {
    
        fprintf(stderr, "Could not open '%s': %s\n", filename, av_err2str(ret));
    
        return 1;
    
    }
    
    }
    
/* Write the stream header, if any. */
    
ret = avformat_write_header(oc, NULL);
    
if (ret < 0) {
    
    fprintf(stderr, "Error occurred when opening output file: %s\n", av_err2str(ret));
    
    return 1;
    
}
    

    
// Setup x264 params
    
x264_param_t param;
    
x264_param_default_preset(&param, "veryfast", "zerolatency");
    
param.i_threads = 1;
    
param.i_width = video_st->codec->width;
    
param.i_height = video_st->codec->height;
    
param.i_fps_num = STREAM_FRAME_RATE; // 30 fps, same as video
    
param.i_fps_den = 1;
    
// Intra refres:
    
param.i_keyint_max = STREAM_FRAME_RATE;
    
param.b_intra_refresh = 1;
    
// Rate control:
    
param.rc.i_rc_method = X264_RC_CRF;
    
param.rc.f_rf_constant = 25;
    
param.rc.f_rf_constant_max = 35;
    
// For streaming:
    
param.b_repeat_headers = 1;
    
param.b_annexb = 1;
    
x264_param_apply_profile(&param, "baseline");
    

    
x264_t* encoder = x264_encoder_open(&param);
    
x264_picture_t pic_in, pic_out;
    
x264_picture_alloc(&pic_in, X264_CSP_I420, video_st->codec->width, video_st->codec->height);
    

    
x264_nal_t* nals;
    
int i_nals;
    

    
// The loop:
    
// 1. Read frames
    
// 2. Decode the frame
    
// 3. Attempt to re-encode using x264
    
// 4. Write the x264 encoded frame using av_interleaved_write_frame
    
while (av_read_frame(pFormatCtx, &packet) >= 0) {
    
    // Is this a packet from the video stream?
    
    if (packet.stream_index == videoStream) {
    
        // Decode video frame
    
        avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
    

    
        // Did we get a video frame?
    
        if (frameFinished) {
    
            sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pic_in.img.plane, pic_in.img.i_stride);
    
            int frame_size = x264_encoder_encode(encoder, &nals, &i_nals, &pic_in, &pic_out);
    

    
            if (frame_size >= 0) {
    
                if (i_nals < 0)
    
                    printf("invalid frame size: %d\n", i_nals);
    
                // write out NALs
    
                for (i = 0; i < i_nals; i++) {
    
                    // initalize a packet
    
                    AVPacket p;
    
                    av_init_packet(&p);
    
                    p.data = nals[i].p_payload;
    
                    p.size = nals[i].i_payload;
    
                    p.stream_index = video_st->index;
    
                    p.flags = AV_PKT_FLAG_KEY;
    
                    p.pts = AV_NOPTS_VALUE;
    
                    p.dts = AV_NOPTS_VALUE;
    
                    ret = av_interleaved_write_frame(oc, &p);
    
                }
    
            }
    
            printf("encoded frame #%d\n", frame_count);
    
            frame_count++;
    
        }
    
    }
    

    
    // Free the packet that was allocated by av_read_frame
    
    av_free_packet(&packet);
    
}
    

    
// Now we free up resources used/close codecs, and finally close our program.

    Here is the implementation for the add_stream() function :

    /* Add an output stream. */
    
static AVStream *add_stream(AVFormatContext *oc, AVCodec **codec, enum AVCodecID codec_id) {
    
    AVCodecContext *c;
    
    AVStream *st;
    
    int r;
    
    /* find the encoder */
    
    *codec = avcodec_find_encoder(codec_id);
    
    if (!(*codec)) {
    
        fprintf(stderr, "Could not find encoder for '%s'\n",
    
                avcodec_get_name(codec_id));
    
        exit(1);
    
    }
    
    st = avformat_new_stream(oc, *codec);
    
    if (!st) {
    
        fprintf(stderr, "Could not allocate stream\n");
    
        exit(1);
    
    }
    
    st->id = oc->nb_streams - 1;
    
    c = st->codec;
    
    switch ((*codec)->type) {
    
    case AVMEDIA_TYPE_AUDIO:
    
        st->id = 1;
    
        c->sample_fmt = AV_SAMPLE_FMT_FLTP;
    
        c->bit_rate = 64000;
    
        c->sample_rate = 44100;
    
        c->channels = 2;
    
        break;
    
    case AVMEDIA_TYPE_VIDEO:
    
        avcodec_get_context_defaults3(c, *codec);
    
        c->codec_id = codec_id;
    
        c->bit_rate = 500*1000;
    
        //c->rc_min_rate = 500*1000;
    
        //c->rc_max_rate = 500*1000;
    
        //c->rc_buffer_size = 500*1000;
    
        /* Resolution must be a multiple of two. */
    
        c->width = 1280;
    
        c->height = 720;
    
        /* timebase: This is the fundamental unit of time (in seconds) in terms
    
         * of which frame timestamps are represented. For fixed-fps content,
    
         * timebase should be 1/framerate and timestamp increments should be
    
         * identical to 1. */
    
        c->time_base.den = STREAM_FRAME_RATE;
    
        c->time_base.num = 1;
    
        c->gop_size = 12; /* emit one intra frame every twelve frames at most */
    
        c->pix_fmt = STREAM_PIX_FMT;
    
        if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
    
            /* just for testing, we also add B frames */
    
            c->max_b_frames = 2;
    
        }
    
        if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
    
            /* Needed to avoid using macroblocks in which some coeffs overflow.
    
             * This does not happen with normal video, it just happens here as
    
             * the motion of the chroma plane does not match the luma plane. */
    
            c->mb_decision = 2;
    
        }
    
        break;
    
    default:
    
        break;
    
    }
    
    /* Some formats want stream headers to be separate. */
    
    if (oc->oformat->flags & AVFMT_GLOBALHEADER)
    
        c->flags |= CODEC_FLAG_GLOBAL_HEADER;
    
    return st;
    
}

    After the encoding is complete, I check the output file output_file.flv. I notice it's size is very large : 101MB and it does not play. If I use ffmpeg to decode/encode the input file, then I get an output file about 83MB in size (which is about the same size as the original .mp4 file used as input). Also, the 83MB output from just using ffmpeg C api, as opposed to using x264 for the encoding step, plays just fine. Does anyone know where I am going wrong ? I have tried researching this for a few days now but with no luck :(. I feel that I am close to making it work, however, I just cannot figure out what I am doing wrong. Thank you !

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