[FFmpeg-devel] [PATCH] avformat/mpjpegdec: add support for X-Timestamp and X-Framerate headers

[Vladimir Sobolev via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

>From a9c2970ea4c06f2503ce0089291c8d0bc1b3da4f Mon Sep 17 00:00:00 2001
From: 350d <350d@example.com>
Date: Sun, 9 Nov 2025 02:06:23 +0200
Subject: [PATCH] avformat/mpjpegdec: add support for X-Timestamp and
X-Framerate headers

Add support for parsing X-Timestamp and X-Framerate headers from
HTTP multipart MJPEG streams. These headers allow servers to provide
accurate timestamps and framerate information for each frame.

Changes:
- Parse X-Timestamp header (in seconds) and set packet PTS/DTS
- Parse X-Framerate/X-FrameRate header and update stream framerate
- Maintain backward compatibility (defaults to 25 fps if not provided)
- Add debug logging for parsed header values

This enables proper timestamp handling for MJPEG streams that provide
timing information in HTTP headers, improving synchronization accuracy.
---
libavformat/mpjpegdec.c | 69 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 65 insertions(+), 4 deletions(-)

diff --git a/libavformat/mpjpegdec.c b/libavformat/mpjpegdec.c
index 125b17585e..c90d7a2ad4 100644
--- a/libavformat/mpjpegdec.c
+++ b/libavformat/mpjpegdec.c
@@ -22,6 +22,9 @@
#include "libavutil/avstring.h"
#include "libavutil/mem.h"
#include "libavutil/opt.h"
+#include "libavutil/parseutils.h"
+#include "libavutil/eval.h"
+#include "libavutil/intfloat.h"
#include "avformat.h"
#include "demux.h"
@@ -34,6 +37,11 @@ typedef struct MPJPEGDemuxContext {
char *searchstr;
int searchstr_len;
int strict_mime_boundary;
+ AVRational framerate; /* framerate from X-Framerate header */
+ int64_t timestamp; /* timestamp from X-Timestamp header */
+ int has_timestamp; /* flag indicating if timestamp was set */
+ int framerate_set; /* flag indicating if framerate was set in header */
+ int framerate_applied; /* flag indicating if framerate was applied to stream */
} MPJPEGDemuxContext;
static void trim_right(char *p)
@@ -97,7 +105,8 @@ static int split_tag_value(char **tag, char **value, char *line)
static int parse_multipart_header(AVIOContext *pb,
int* size,
const char* expected_boundary,
- void *log_ctx);
+ void *log_ctx,
+ MPJPEGDemuxContext *mpjpeg);
static int mpjpeg_read_close(AVFormatContext *s)
{
@@ -118,7 +127,7 @@ static int mpjpeg_read_probe(const AVProbeData *p)
ffio_init_read_context(&pb, p->buf, p->buf_size);
- ret = (parse_multipart_header(&pb.pub, &size, "--", NULL) >= 0) ? AVPROBE_SCORE_MAX : 0;
+ ret = (parse_multipart_header(&pb.pub, &size, "--", NULL, NULL) >= 0) ? AVPROBE_SCORE_MAX : 0;
return ret;
}
@@ -146,6 +155,12 @@ static int mpjpeg_read_header(AVFormatContext *s)
st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
st->codecpar->codec_id = AV_CODEC_ID_MJPEG;
+ /* Default framerate is 25 fps, will be updated from headers if available */
+ MPJPEGDemuxContext *mpjpeg = s->priv_data;
+ mpjpeg->framerate = (AVRational){25, 1};
+ mpjpeg->framerate_set = 0;
+ mpjpeg->framerate_applied = 0;
+ mpjpeg->has_timestamp = 0;
avpriv_set_pts_info(st, 60, 1, 25);
avio_seek(s->pb, pos, SEEK_SET);
@@ -167,7 +182,8 @@ static int parse_content_length(const char *value)
static int parse_multipart_header(AVIOContext *pb,
int* size,
const char* expected_boundary,
- void *log_ctx)
+ void *log_ctx,
+ MPJPEGDemuxContext *mpjpeg)
{
char line[128];
int found_content_type = 0;
@@ -235,6 +251,33 @@ static int parse_multipart_header(AVIOContext *pb,
av_log(log_ctx, AV_LOG_WARNING,
"Invalid Content-Length value : %s\n",
value);
+ } else if (mpjpeg && !av_strcasecmp(tag, "X-Timestamp")) {
+ double ts = av_strtod(value, NULL);
+ if (!isnan(ts) && isfinite(ts)) {
+ /* X-Timestamp is in seconds, convert to AV_TIME_BASE */
+ mpjpeg->timestamp = (int64_t)(ts * AV_TIME_BASE);
+ mpjpeg->has_timestamp = 1;
+ if (log_ctx)
+ av_log(log_ctx, AV_LOG_DEBUG,
+ "Parsed X-Timestamp: %s -> %"PRId64" (%.6f seconds)\n",
+ value, mpjpeg->timestamp, ts);
+ } else if (log_ctx) {
+ av_log(log_ctx, AV_LOG_WARNING,
+ "Invalid X-Timestamp value : %s\n", value);
+ }
+ } else if (mpjpeg && (!av_strcasecmp(tag, "X-Framerate") || !av_strcasecmp(tag, "X-FrameRate"))) {
+ AVRational fps = {0};
+ if (av_parse_video_rate(&fps, value) >= 0 && fps.num > 0 && fps.den > 0) {
+ mpjpeg->framerate = fps;
+ mpjpeg->framerate_set = 1;
+ if (log_ctx)
+ av_log(log_ctx, AV_LOG_DEBUG,
+ "Parsed X-Framerate: %s -> %d/%d fps\n",
+ value, fps.num, fps.den);
+ } else if (log_ctx) {
+ av_log(log_ctx, AV_LOG_WARNING,
+ "Invalid X-Framerate value : %s\n", value);
+ }
}
}
@@ -311,10 +354,21 @@ static int mpjpeg_read_packet(AVFormatContext *s, AVPacket *pkt)
mpjpeg->searchstr_len = strlen(mpjpeg->searchstr);
}
- ret = parse_multipart_header(s->pb, &size, mpjpeg->boundary, s);
+ /* Reset timestamp flag for each packet */
+ mpjpeg->has_timestamp = 0;
+
+ ret = parse_multipart_header(s->pb, &size, mpjpeg->boundary, s, mpjpeg);
if (ret < 0)
return ret;
+ /* Update framerate if it was set in header and hasn't been applied yet */
+ if (mpjpeg->framerate_set && !mpjpeg->framerate_applied && s->nb_streams > 0) {
+ AVStream *st = s->streams[0];
+ st->avg_frame_rate = mpjpeg->framerate;
+ avpriv_set_pts_info(st, 60, mpjpeg->framerate.den, mpjpeg->framerate.num);
+ mpjpeg->framerate_applied = 1;
+ }
+
if (size > 0) {
/* size has been provided to us in MIME header */
ret = av_get_packet(s->pb, pkt, size);
@@ -353,6 +407,13 @@ static int mpjpeg_read_packet(AVFormatContext *s, AVPacket *pkt)
}
}
+ /* Set timestamp from X-Timestamp header if available */
+ if (ret >= 0 && mpjpeg->has_timestamp && s->nb_streams > 0) {
+ AVStream *st = s->streams[0];
+ pkt->pts = av_rescale_q(mpjpeg->timestamp, AV_TIME_BASE_Q, st->time_base);
+ pkt->dts = pkt->pts;
+ }
+
return ret;
}
-- 
2.50.1 (Apple Git-155)


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