On Wed, Apr 30, 2025 at 09:25:19AM +0200, Dietmar Maurer wrote:
> This patch implements H264 support for VNC. The RFB protocol
> extension is defined in:
>
> https://github.com/rfbproto/rfbproto/blob/master/rfbproto.rst#open-h-264-encoding
>
> Currently the Gstreamer x264enc plugin (software encoder) is used
> to encode the video stream.
>
> The gstreamer pipe is:
>
> appsrc -> videoconvert -> x264enc -> appsink
>
> Note: videoconvert is required for RGBx to YUV420 conversion.
>
> The code still use the VNC server framebuffer change detection,
> and only encodes and sends video frames if there are changes.
>
> Signed-off-by: Dietmar Maurer <diet...@proxmox.com>
> ---
> ui/meson.build | 1 +
> ui/vnc-enc-h264.c | 255 ++++++++++++++++++++++++++++++++++++++++++++++
> ui/vnc-jobs.c | 53 +++++++---
> ui/vnc.c | 37 ++++++-
> ui/vnc.h | 21 ++++
> 5 files changed, 350 insertions(+), 17 deletions(-)
> create mode 100644 ui/vnc-enc-h264.c
> diff --git a/ui/vnc-enc-h264.c b/ui/vnc-enc-h264.c
> new file mode 100644
> index 0000000000..26e8c19270
> --- /dev/null
> +++ b/ui/vnc-enc-h264.c
> @@ -0,0 +1,255 @@
> +/*
> + * QEMU VNC display driver: H264 encoding
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include "qemu/osdep.h"
> +#include "vnc.h"
> +
> +#include <gst/gst.h>
> +
> +static void destroy_encoder_context(VncState *vs)
> +{
> + gst_clear_object(&vs->h264->source);
> + gst_clear_object(&vs->h264->convert);
> + gst_clear_object(&vs->h264->gst_encoder);
> + gst_clear_object(&vs->h264->sink);
> + gst_clear_object(&vs->h264->pipeline);
> +}
> +
> +static bool create_encoder_context(VncState *vs, int w, int h)
> +{
> + g_autoptr(GstCaps) source_caps = NULL;
> + GstStateChangeReturn state_change_ret;
> +
> + g_assert(vs->h264 != NULL);
> +
> + if (vs->h264->sink && w == vs->h264->width && h == vs->h264->height) {
> + return TRUE;
> + }
> +
> + destroy_encoder_context(vs);
> +
> + vs->h264->width = w;
> + vs->h264->height = h;
> +
> + vs->h264->source = gst_element_factory_make("appsrc", "source");
> + if (!vs->h264->source) {
> + VNC_DEBUG("Could not create gst source\n");
> + goto error;
> + }
> +
> + vs->h264->convert = gst_element_factory_make("videoconvert", "convert");
> + if (!vs->h264->convert) {
> + VNC_DEBUG("Could not create gst convert element\n");
> + goto error;
> + }
> +
> + vs->h264->gst_encoder = gst_element_factory_make("x264enc",
> "gst-encoder");
> + if (!vs->h264->gst_encoder) {
> + VNC_DEBUG("Could not create gst x264 encoder\n");
> + goto error;
> + }
> +
> + g_object_set(
> + vs->h264->gst_encoder,
> + "tune", 4, /* zerolatency */
> + /*
> + * fix for zerolatency with novnc (without, noVNC displays
> + * green stripes)
> + */
> + "threads", 1,
> + "pass", 5, /* Constant Quality */
> + "quantizer", 26,
> + /* avoid access unit delimiters (Nal Unit Type 9) - not required */
> + "aud", false,
> + NULL);
> +
> + vs->h264->sink = gst_element_factory_make("appsink", "sink");
> + if (!vs->h264->sink) {
> + VNC_DEBUG("Could not create gst sink\n");
> + goto error;
> + }
> +
> + vs->h264->pipeline = gst_pipeline_new("vnc-h264-pipeline");
> + if (!vs->h264->pipeline) {
> + VNC_DEBUG("Could not create gst pipeline\n");
> + goto error;
> + }
> +
> + gst_object_ref(vs->h264->source);
> + if (!gst_bin_add(GST_BIN(vs->h264->pipeline), vs->h264->source)) {
> + gst_object_unref(vs->h264->source);
> + VNC_DEBUG("Could not add source to gst pipeline\n");
> + goto error;
> + }
> +
> + gst_object_ref(vs->h264->convert);
> + if (!gst_bin_add(GST_BIN(vs->h264->pipeline), vs->h264->convert)) {
> + gst_object_unref(vs->h264->convert);
> + VNC_DEBUG("Could not add convert to gst pipeline\n");
> + goto error;
> + }
> +
> + gst_object_ref(vs->h264->gst_encoder);
> + if (!gst_bin_add(GST_BIN(vs->h264->pipeline), vs->h264->gst_encoder)) {
> + gst_object_unref(vs->h264->gst_encoder);
> + VNC_DEBUG("Could not add encoder to gst pipeline\n");
> + goto error;
> + }
> +
> + gst_object_ref(vs->h264->sink);
> + if (!gst_bin_add(GST_BIN(vs->h264->pipeline), vs->h264->sink)) {
> + gst_object_unref(vs->h264->sink);
> + VNC_DEBUG("Could not add sink to gst pipeline\n");
> + goto error;
> + }
> +
> + source_caps = gst_caps_new_simple(
> + "video/x-raw",
> + "format", G_TYPE_STRING, "BGRx",
> + "framerate", GST_TYPE_FRACTION, 33, 1,
> + "width", G_TYPE_INT, w,
> + "height", G_TYPE_INT, h,
> + NULL);
> +
> + if (!source_caps) {
> + VNC_DEBUG("Could not create source caps filter\n");
> + goto error;
> + }
> +
> + g_object_set(vs->h264->source, "caps", source_caps, NULL);
> +
> + if (gst_element_link_many(
> + vs->h264->source,
> + vs->h264->convert,
> + vs->h264->gst_encoder,
> + vs->h264->sink,
> + NULL
> + ) != TRUE) {
> + VNC_DEBUG("Elements could not be linked.\n");
> + goto error;
> + }
> +
> + /* Start playing */
> + state_change_ret = gst_element_set_state(
> + vs->h264->pipeline, GST_STATE_PLAYING);
> +
> + if (state_change_ret == GST_STATE_CHANGE_FAILURE) {
> + VNC_DEBUG("Unable to set the pipeline to the playing state.\n");
> + goto error;
> + }
> +
> + return TRUE;
> +
> + error:
> + destroy_encoder_context(vs);
> + return FALSE;
> +}
> +
> +bool vnc_h264_encoder_init(VncState *vs)
> +{
> + g_assert(vs->h264 == NULL);
> +
> + vs->h264 = g_new0(VncH264, 1);
> +
> + return true;
> +}
> +
> +/*
> + * Returns the number of generated framebuffer updates,
> + * or -1 in case of errors
> + */
> +int vnc_h264_send_framebuffer_update(VncState *vs)
> +{
> + int n = 0;
> + int rdb_h264_flags = 0;
> + int width, height;
> + uint8_t *src_data_ptr = NULL;
> + size_t src_data_size;
> + GstFlowReturn flow_ret = GST_FLOW_ERROR;
> + GstBuffer *src_buffer = NULL;
> +
> + g_assert(vs->h264 != NULL);
> + g_assert(vs->vd != NULL);
> + g_assert(vs->vd->server != NULL);
> +
> + width = pixman_image_get_width(vs->vd->server);
> + height = pixman_image_get_height(vs->vd->server);
> +
> + g_assert(width == vs->client_width);
> + g_assert(height == vs->client_height);
> +
> + if (vs->h264->sink) {
> + if (width != vs->h264->width || height != vs->h264->height) {
> + rdb_h264_flags = 2;
> + }
> + } else {
> + rdb_h264_flags = 2;
> + }
> +
> + if (!create_encoder_context(vs, width, height)) {
> + VNC_DEBUG("Create encoder context failed\n");
> + return -1;
> + }
> +
> + g_assert(vs->h264->sink != NULL);
> +
> + src_data_ptr = vnc_server_fb_ptr(vs->vd, 0, 0);
> + src_data_size = width * height * VNC_SERVER_FB_BYTES;
> +
> + src_buffer = gst_buffer_new_wrapped_full(
> + 0, src_data_ptr, src_data_size, 0, src_data_size, NULL, NULL);
> +
> + g_signal_emit_by_name(
> + vs->h264->source, "push-buffer", src_buffer, &flow_ret);
> +
> + if (flow_ret != GST_FLOW_OK) {
> + VNC_DEBUG("gst appsrc push buffer failed\n");
> + return -1;
> + }
> +
> + do {
> + GstSample *sample = NULL;
> + GstMapInfo map;
> + GstBuffer *out_buffer;
> +
> + /* Retrieve the buffer */
> + g_signal_emit_by_name(vs->h264->sink, "try-pull-sample", 0, &sample);
> + if (!sample) {
> + break;
> + }
> + out_buffer = gst_sample_get_buffer(sample);
> + if (gst_buffer_map(out_buffer, &map, 0)) {
> + vnc_framebuffer_update(vs, 0, 0, width, height,
> VNC_ENCODING_H264);
> + vnc_write_s32(vs, map.size); /* write data length */
> + vnc_write_s32(vs, rdb_h264_flags); /* write flags */
> + rdb_h264_flags = 0;
> +
> + VNC_DEBUG("GST vnc_h264_update send %ld\n", map.size);
> +
> + vnc_write(vs, map.data, map.size);
> +
> + gst_buffer_unmap(out_buffer, &map);
> +
> + n += 1;
> + } else {
> + VNC_DEBUG("unable to map sample\n");
> + }
> + gst_sample_unref(sample);
> + } while (true);
> +
> + return n;
> +}
> +
> +void vnc_h264_clear(VncState *vs)
> +{
> + if (!vs->h264) {
> + return;
> + }
> +
> + destroy_encoder_context(vs);
> +
> + g_clear_pointer(&vs->h264, g_free);
> +}
> diff --git a/ui/vnc.c b/ui/vnc.c
> index 9e097dc4b4..ba71589c6f 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -4289,6 +4320,10 @@ int vnc_init_func(void *opaque, QemuOpts *opts, Error
> **errp)
> Error *local_err = NULL;
> char *id = (char *)qemu_opts_id(opts);
>
> +#ifdef CONFIG_GSTREAMER
> + gst_init(NULL, NULL);
This method aborts the process on failure. We need to use
gst_init_check(NULL, NULL, &err)
and report the 'err' result with error_report() so it
integrates with QEMU's normal error reporting mechanisms.
> @@ -625,6 +642,10 @@ int vnc_zrle_send_framebuffer_update(VncState *vs, int
> x, int y, int w, int h);
> int vnc_zywrle_send_framebuffer_update(VncState *vs, int x, int y, int w,
> int h);
> void vnc_zrle_clear(VncState *vs);
>
> +bool vnc_h264_encoder_init(VncState *vs);
> +int vnc_h264_send_framebuffer_update(VncState *vs);
> +void vnc_h264_clear(VncState *vs);
These ought to be wrapped in '#ifdef CONFIG_GSTREAMER' too, so that is
obvious they're conditionally available, and it'll trigger a compiler
error if someone tries to call them outside a matching #ifdef
> +
> /* vnc-clipboard.c */
> void vnc_server_cut_text_caps(VncState *vs);
> void vnc_client_cut_text(VncState *vs, size_t len, uint8_t *text);
> --
> 2.39.5
>
>
With regards,
Daniel
--
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