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Autres articles (50)
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XMP PHP
13 mai 2011, parDixit Wikipedia, XMP signifie :
Extensible Metadata Platform ou XMP est un format de métadonnées basé sur XML utilisé dans les applications PDF, de photographie et de graphisme. Il a été lancé par Adobe Systems en avril 2001 en étant intégré à la version 5.0 d’Adobe Acrobat.
Étant basé sur XML, il gère un ensemble de tags dynamiques pour l’utilisation dans le cadre du Web sémantique.
XMP permet d’enregistrer sous forme d’un document XML des informations relatives à un fichier : titre, auteur, historique (...) -
Déploiements possibles
31 janvier 2010, parDeux types de déploiements sont envisageable dépendant de deux aspects : La méthode d’installation envisagée (en standalone ou en ferme) ; Le nombre d’encodages journaliers et la fréquentation envisagés ;
L’encodage de vidéos est un processus lourd consommant énormément de ressources système (CPU et RAM), il est nécessaire de prendre tout cela en considération. Ce système n’est donc possible que sur un ou plusieurs serveurs dédiés.
Version mono serveur
La version mono serveur consiste à n’utiliser qu’une (...) -
Ajouter notes et légendes aux images
7 février 2011, parPour pouvoir ajouter notes et légendes aux images, la première étape est d’installer le plugin "Légendes".
Une fois le plugin activé, vous pouvez le configurer dans l’espace de configuration afin de modifier les droits de création / modification et de suppression des notes. Par défaut seuls les administrateurs du site peuvent ajouter des notes aux images.
Modification lors de l’ajout d’un média
Lors de l’ajout d’un média de type "image" un nouveau bouton apparait au dessus de la prévisualisation (...)
Sur d’autres sites (5435)
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Seeking in Libav / FFMPEG a DASH stream
23 janvier 2018, par Glen RhodesRecently, the functionality for playing DASH format files (mpd) was added to Libav. I’m trying to determine the best way to seek forward in the stream.
When I use av_seek_frame, it does go to the correct time, but there’s a considerable delay which makes me think it’s not properly jumping to a segment / byte offset in the HTTP request, but rather just downloading with all its might until it arrives at the correct timestamp.
int ret = av_seek_frame(is->pFormatCtx, stream_index, seek_target, is->seek_flags);When I use avformat_seek_file, it only seems to go forward several seconds before just continuing to play. So if I start playback, and then seek to 50 seconds, it will jump to something like 12. If I do the same seek again, it’ll jump further ahead, but still not 50.. however if it eventually gets to 50, then I do avformat_seek_file, it will successfully jump back to 50 no problem. So it’s like it tries, and gives up.
int ret = avformat_seek_file(is->pFormatCtx, stream_index, INT64_MIN, tm, INT64_MAX, 0);Does anyone know how seeking is managed in the Libav dash playback ?
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libavformat/libavcodec providing invalid container header
14 décembre 2017, par seanr8I’m using libavcodec to encode a stream to h264 and libavformat to store it in an mp4. The resulting container has an invalid header that can be played in VLC, but not any other player.
I’ve found that using the mp4 container and the "mpeg4" codec produces a valid mp4 file, but using libx265 (HEVC) or the libx264 codec produces invalid mp4s.
I can use
ffmpeg -i invalid.mp4 -vcodec copy valid.mp4and I get a file of almost the exact same size, but in a valid container.Examples of these files are here : Broken file and
Repaied file [use the download links in the upper right to examine]I used a hex editor to see the differences in the headers of the two files and the invalid one is 1 byte smaller than the valid one.
The code I’m using to open the container and codec and to write the header is here :
AVOutputFormat *container_format;
AVFormatContext *container_format_context;
AVStream *video_stream;
int ret;
/* allocate the output media context */
avformat_alloc_output_context2(&container_format_context, NULL, NULL, out_file);
if (!container_format_context) {
log(INFO, "Unable to determine container format from filename, exiting\n");
exit(1);
}
else {
log(INFO, "Using container %s\n", container_format_context->oformat->name);
}
if (!container_format_context) {
log(ERROR, "Could not build container format context. Encoding failed.");
exit(1);
}
container_format = container_format_context->oformat;
/* Pull codec based on name */
AVCodec* codec = avcodec_find_encoder_by_name(codec_name);
if (codec == NULL) {
log(ERROR, "Failed to locate codec \"%s\".",
codec_name);
exit(1);
}
/* create stream */
video_stream = NULL;
video_stream = avformat_new_stream(container_format_context, codec);
if (!video_stream) {
log(ERROR, "Could not allocate encoder stream. Cannot continue.\n");
exit(1);
}
video_stream->id = container_format_context->nb_streams - 1;
video_stream->time_base = video_stream->codec->time_base = (AVRational) { 1, 25};
av_dump_format(container_format_context, 0, out_file, 1);
/* Retrieve encoding context */
AVCodecContext* avcodec_context = video_stream->codec;
if (avcodec_context == NULL) {
log(ERROR, "Failed to allocate context for "
"codec \"%s\".", codec_name);
exit(1);
}
/* Init context with encoding parameters */
avcodec_context->bit_rate = bitrate;
avcodec_context->width = width;
avcodec_context->height = height;
avcodec_context->gop_size = 10;
avcodec_context->max_b_frames = 1;
avcodec_context->qmax = 31;
avcodec_context->qmin = 2;
avcodec_context->pix_fmt = AV_PIX_FMT_YUV420P;
av_dump_format(container_format_context, 0, out_file, 1);
/* Open codec for use */
if (avcodec_open2(avcodec_context, codec, NULL) < 0) {
log(ERROR, "Failed to open codec \"%s\".", codec_name);
exit(1);
}
/* Allocate corresponding frame */
AVFrame* frame = av_frame_alloc();
if (frame == NULL) {
exit(1);
}
/* Copy necessary data for frame from avcodec_context */
frame->format = avcodec_context->pix_fmt;
frame->width = avcodec_context->width;
frame->height = avcodec_context->height;
/* Allocate actual backing data for frame */
if (av_image_alloc(frame->data, frame->linesize, frame->width,
frame->height, frame->format, 32) < 0) {
exit(1);
}
/* open the output file, if the container needs it */
if (!(container_format->flags & AVFMT_NOFILE)) {
ret = avio_open(&container_format_context->pb, out_file, AVIO_FLAG_WRITE);
if (ret < 0) {
log(ERROR, "Error occurred while opening output file: %s\n",
av_err2str(ret));
exit(1);
}
}
/* write the stream header, if needed */
ret = avformat_write_header(container_format_context, NULL);
if (ret < 0) {
log(ERROR, "Error occurred while writing output file header: %s\n",
av_err2str(ret));
}The code to encode a frame is here :
/* Init video packet */
AVPacket packet;
av_init_packet(&packet);
/* Request that encoder allocate data for packet */
packet.data = NULL;
packet.size = 0;
/* Write frame to video */
int got_data;
if (avcodec_encode_video2(avcontext, &packet, frame, &got_data) < 0) {
log(WARNING, "Error encoding frame #%" PRId64,
video_struct->next_pts);
return -1;
}
/* Write corresponding data to file */
if (got_data) {
if (packet.pts != AV_NOPTS_VALUE) {
packet.pts = av_rescale_q(packet.pts, video_struct->output_stream->codec->time_base, video_struct->output_stream->time_base);
}
if (packet.dts != AV_NOPTS_VALUE) {
packet.dts = av_rescale_q(packet.dts, video_struct->output_stream->codec->time_base, video_struct->output_stream->time_base);
}
write_packet(video_struct, &packet, packet.size);
av_packet_unref(&packet);
}And the code to write the packet to the video stream :
static int write_packet(video_struct* video, void* data, int size) {
int ret;
/* use AVStream is not null, otherwise write to output fd */
AVPacket *pkt = (AVPacket*) data;
pkt->stream_index = video->output_stream->index;
ret = av_interleaved_write_frame(video->container_format_context, pkt);
if (ret != 0) {
return -1;
}
/* Data was written successfully */
return ret;
} -
libavformat/libavcodec providing invalid container header
14 décembre 2017, par seanr8I’m using libavcodec to encode a stream to h264 and libavformat to store it in an mp4. The resulting container has an invalid header that can be played in VLC, but not any other player.
I’ve found that using the mp4 container and the "mpeg4" codec produces a valid mp4 file, but using libx265 (HEVC) or the libx264 codec produces invalid mp4s.
I can use
ffmpeg -i invalid.mp4 -vcodec copy valid.mp4and I get a file of almost the exact same size, but in a valid container.Examples of these files are here : Broken file and
Repaied file [use the download links in the upper right to examine]I used a hex editor to see the differences in the headers of the two files and the invalid one is 1 byte smaller than the valid one.
The code I’m using to open the container and codec and to write the header is here :
AVOutputFormat *container_format;
AVFormatContext *container_format_context;
AVStream *video_stream;
int ret;
/* allocate the output media context */
avformat_alloc_output_context2(&container_format_context, NULL, NULL, out_file);
if (!container_format_context) {
log(INFO, "Unable to determine container format from filename, exiting\n");
exit(1);
}
else {
log(INFO, "Using container %s\n", container_format_context->oformat->name);
}
if (!container_format_context) {
log(ERROR, "Could not build container format context. Encoding failed.");
exit(1);
}
container_format = container_format_context->oformat;
/* Pull codec based on name */
AVCodec* codec = avcodec_find_encoder_by_name(codec_name);
if (codec == NULL) {
log(ERROR, "Failed to locate codec \"%s\".",
codec_name);
exit(1);
}
/* create stream */
video_stream = NULL;
video_stream = avformat_new_stream(container_format_context, codec);
if (!video_stream) {
log(ERROR, "Could not allocate encoder stream. Cannot continue.\n");
exit(1);
}
video_stream->id = container_format_context->nb_streams - 1;
video_stream->time_base = video_stream->codec->time_base = (AVRational) { 1, 25};
av_dump_format(container_format_context, 0, out_file, 1);
/* Retrieve encoding context */
AVCodecContext* avcodec_context = video_stream->codec;
if (avcodec_context == NULL) {
log(ERROR, "Failed to allocate context for "
"codec \"%s\".", codec_name);
exit(1);
}
/* Init context with encoding parameters */
avcodec_context->bit_rate = bitrate;
avcodec_context->width = width;
avcodec_context->height = height;
avcodec_context->gop_size = 10;
avcodec_context->max_b_frames = 1;
avcodec_context->qmax = 31;
avcodec_context->qmin = 2;
avcodec_context->pix_fmt = AV_PIX_FMT_YUV420P;
av_dump_format(container_format_context, 0, out_file, 1);
/* Open codec for use */
if (avcodec_open2(avcodec_context, codec, NULL) < 0) {
log(ERROR, "Failed to open codec \"%s\".", codec_name);
exit(1);
}
/* Allocate corresponding frame */
AVFrame* frame = av_frame_alloc();
if (frame == NULL) {
exit(1);
}
/* Copy necessary data for frame from avcodec_context */
frame->format = avcodec_context->pix_fmt;
frame->width = avcodec_context->width;
frame->height = avcodec_context->height;
/* Allocate actual backing data for frame */
if (av_image_alloc(frame->data, frame->linesize, frame->width,
frame->height, frame->format, 32) < 0) {
exit(1);
}
/* open the output file, if the container needs it */
if (!(container_format->flags & AVFMT_NOFILE)) {
ret = avio_open(&container_format_context->pb, out_file, AVIO_FLAG_WRITE);
if (ret < 0) {
log(ERROR, "Error occurred while opening output file: %s\n",
av_err2str(ret));
exit(1);
}
}
/* write the stream header, if needed */
ret = avformat_write_header(container_format_context, NULL);
if (ret < 0) {
log(ERROR, "Error occurred while writing output file header: %s\n",
av_err2str(ret));
}The code to encode a frame is here :
/* Init video packet */
AVPacket packet;
av_init_packet(&packet);
/* Request that encoder allocate data for packet */
packet.data = NULL;
packet.size = 0;
/* Write frame to video */
int got_data;
if (avcodec_encode_video2(avcontext, &packet, frame, &got_data) < 0) {
log(WARNING, "Error encoding frame #%" PRId64,
video_struct->next_pts);
return -1;
}
/* Write corresponding data to file */
if (got_data) {
if (packet.pts != AV_NOPTS_VALUE) {
packet.pts = av_rescale_q(packet.pts, video_struct->output_stream->codec->time_base, video_struct->output_stream->time_base);
}
if (packet.dts != AV_NOPTS_VALUE) {
packet.dts = av_rescale_q(packet.dts, video_struct->output_stream->codec->time_base, video_struct->output_stream->time_base);
}
write_packet(video_struct, &packet, packet.size);
av_packet_unref(&packet);
}And the code to write the packet to the video stream :
static int write_packet(video_struct* video, void* data, int size) {
int ret;
/* use AVStream is not null, otherwise write to output fd */
AVPacket *pkt = (AVPacket*) data;
pkt->stream_index = video->output_stream->index;
ret = av_interleaved_write_frame(video->container_format_context, pkt);
if (ret != 0) {
return -1;
}
/* Data was written successfully */
return ret;
}
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