examples: Add a VA-API transcode example.

Usage is:
./vaapi_transcode input_stream codec output_stream
For example:
- ./vaapi_transcode input.mp4 h264_vaapi output_h264.mp4
- ./vaapi_transcode input.mp4 vp8_vaapi output_vp8.ivf

Does not handle resolution changes on the input stream.

Signed-off-by: Jun Zhao <jun.zhao@intel.com>
Signed-off-by: Liu, Kaixuan <kaixuan.liu@intel.com>
Signed-off-by: Mark Thompson <sw@jkqxz.net>

configure

@@ -1526,6 +1526,7 @@ EXAMPLE_LIST="
     transcode_aac_example
     transcoding_example
     vaapi_encode_example
+    vaapi_transcode_example
 "
 
 EXTERNAL_AUTODETECT_LIBRARY_LIST="
@@ -3320,6 +3321,7 @@ scaling_video_example_deps="avutil swscale"
 transcode_aac_example_deps="avcodec avformat swresample"
 transcoding_example_deps="avfilter avcodec avformat avutil"
 vaapi_encode_example_deps="avcodec avutil h264_vaapi_encoder"
+vaapi_transcode_example_deps="avcodec avformat avutil h264_vaapi_encoder"
 
 # EXTRALIBS_LIST
 cpu_init_extralibs="pthreads_extralibs"

doc/examples/Makefile

@@ -20,6 +20,7 @@ EXAMPLES-$(CONFIG_SCALING_VIDEO_EXAMPLE)     += scaling_video
 EXAMPLES-$(CONFIG_TRANSCODE_AAC_EXAMPLE)     += transcode_aac
 EXAMPLES-$(CONFIG_TRANSCODING_EXAMPLE)       += transcoding
 EXAMPLES-$(CONFIG_VAAPI_ENCODE_EXAMPLE)      += vaapi_encode
+EXAMPLES-$(CONFIG_VAAPI_TRANSCODE_EXAMPLE)   += vaapi_transcode
 
 EXAMPLES       := $(EXAMPLES-yes:%=doc/examples/%$(PROGSSUF)$(EXESUF))
 EXAMPLES_G     := $(EXAMPLES-yes:%=doc/examples/%$(PROGSSUF)_g$(EXESUF))

doc/examples/vaapi_transcode.c

@@ -0,0 +1,306 @@
+/*
+ * Video Acceleration API (video transcoding) transcode sample
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * Intel VAAPI-accelerated transcoding example.
+ *
+ * @example vaapi_transcode.c
+ * This example shows how to do VAAPI-accelerated transcoding.
+ * Usage: vaapi_transcode input_stream codec output_stream
+ * e.g: - vaapi_transcode input.mp4 h264_vaapi output_h264.mp4
+ *      - vaapi_transcode input.mp4 vp9_vaapi output_vp9.ivf
+ */
+
+#include <stdio.h>
+#include <errno.h>
+
+#include <libavutil/hwcontext.h>
+#include <libavcodec/avcodec.h>
+#include <libavformat/avformat.h>
+
+static AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
+static AVBufferRef *hw_device_ctx = NULL;
+static AVCodecContext *decoder_ctx = NULL, *encoder_ctx = NULL;
+static int video_stream = -1;
+static AVStream *ost;
+static int initialized = 0;
+
+static enum AVPixelFormat get_vaapi_format(AVCodecContext *ctx,
+                                           const enum AVPixelFormat *pix_fmts)
+{
+    const enum AVPixelFormat *p;
+
+    for (p = pix_fmts; *p != AV_PIX_FMT_NONE; p++) {
+        if (*p == AV_PIX_FMT_VAAPI)
+            return *p;
+    }
+
+    fprintf(stderr, "Unable to decode this file using VA-API.\n");
+    return AV_PIX_FMT_NONE;
+}
+
+static int open_input_file(const char *filename)
+{
+    int ret;
+    AVCodec *decoder = NULL;
+    AVStream *video = NULL;
+
+    if ((ret = avformat_open_input(&ifmt_ctx, filename, NULL, NULL)) < 0) {
+        fprintf(stderr, "Cannot open input file '%s', Error code: %s\n",
+                filename, av_err2str(ret));
+        return ret;
+    }
+
+    if ((ret = avformat_find_stream_info(ifmt_ctx, NULL)) < 0) {
+        fprintf(stderr, "Cannot find input stream information. Error code: %s\n",
+                av_err2str(ret));
+        return ret;
+    }
+
+    ret = av_find_best_stream(ifmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &decoder, 0);
+    if (ret < 0) {
+        fprintf(stderr, "Cannot find a video stream in the input file. "
+                "Error code: %s\n", av_err2str(ret));
+        return ret;
+    }
+    video_stream = ret;
+
+    if (!(decoder_ctx = avcodec_alloc_context3(decoder)))
+        return AVERROR(ENOMEM);
+
+    video = ifmt_ctx->streams[video_stream];
+    if ((ret = avcodec_parameters_to_context(decoder_ctx, video->codecpar)) < 0) {
+        fprintf(stderr, "avcodec_parameters_to_context error. Error code: %s\n",
+                av_err2str(ret));
+        return ret;
+    }
+
+    decoder_ctx->hw_device_ctx = av_buffer_ref(hw_device_ctx);
+    if (!decoder_ctx->hw_device_ctx) {
+        fprintf(stderr, "A hardware device reference create failed.\n");
+        return AVERROR(ENOMEM);
+    }
+    decoder_ctx->get_format    = get_vaapi_format;
+
+    if ((ret = avcodec_open2(decoder_ctx, decoder, NULL)) < 0)
+        fprintf(stderr, "Failed to open codec for decoding. Error code: %s\n",
+                av_err2str(ret));
+
+    return ret;
+}
+
+static int encode_write(AVFrame *frame)
+{
+    int ret = 0;
+    AVPacket enc_pkt;
+
+    av_init_packet(&enc_pkt);
+    enc_pkt.data = NULL;
+    enc_pkt.size = 0;
+
+    if ((ret = avcodec_send_frame(encoder_ctx, frame)) < 0) {
+        fprintf(stderr, "Error during encoding. Error code: %s\n", av_err2str(ret));
+        goto end;
+    }
+    while (1) {
+        ret = avcodec_receive_packet(encoder_ctx, &enc_pkt);
+        if (ret)
+            break;
+
+        enc_pkt.stream_index = 0;
+        av_packet_rescale_ts(&enc_pkt, ifmt_ctx->streams[video_stream]->time_base,
+                             ofmt_ctx->streams[0]->time_base);
+        ret = av_interleaved_write_frame(ofmt_ctx, &enc_pkt);
+        if (ret < 0) {
+            fprintf(stderr, "Error during writing data to output file. "
+                    "Error code: %s\n", av_err2str(ret));
+            return -1;
+        }
+    }
+
+end:
+    if (ret == AVERROR_EOF)
+        return 0;
+    ret = ((ret == AVERROR(EAGAIN)) ? 0:-1);
+    return ret;
+}
+
+static int dec_enc(AVPacket *pkt, AVCodec *enc_codec)
+{
+    AVFrame *frame;
+    int ret = 0;
+
+    ret = avcodec_send_packet(decoder_ctx, pkt);
+    if (ret < 0) {
+        fprintf(stderr, "Error during decoding. Error code: %s\n", av_err2str(ret));
+        return ret;
+    }
+
+    while (ret >= 0) {
+        if (!(frame = av_frame_alloc()))
+            return AVERROR(ENOMEM);
+
+        ret = avcodec_receive_frame(decoder_ctx, frame);
+        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
+            av_frame_free(&frame);
+            return 0;
+        } else if (ret < 0) {
+            fprintf(stderr, "Error while decoding. Error code: %s\n", av_err2str(ret));
+            goto fail;
+        }
+
+        if (!initialized) {
+            /* we need to ref hw_frames_ctx of decoder to initialize encoder's codec.
+               Only after we get a decoded frame, can we obtain its hw_frames_ctx */
+            encoder_ctx->hw_frames_ctx = av_buffer_ref(decoder_ctx->hw_frames_ctx);
+            if (!encoder_ctx->hw_frames_ctx) {
+                ret = AVERROR(ENOMEM);
+                goto fail;
+            }
+            /* set AVCodecContext Parameters for encoder, here we keep them stay
+             * the same as decoder.
+             * xxx: now the the sample can't handle resolution change case.
+             */
+            encoder_ctx->time_base = av_inv_q(decoder_ctx->framerate);
+            encoder_ctx->pix_fmt   = AV_PIX_FMT_VAAPI;
+            encoder_ctx->width     = decoder_ctx->width;
+            encoder_ctx->height    = decoder_ctx->height;
+
+            if ((ret = avcodec_open2(encoder_ctx, enc_codec, NULL)) < 0) {
+                fprintf(stderr, "Failed to open encode codec. Error code: %s\n",
+                        av_err2str(ret));
+                goto fail;
+            }
+
+            if (!(ost = avformat_new_stream(ofmt_ctx, enc_codec))) {
+                fprintf(stderr, "Failed to allocate stream for output format.\n");
+                ret = AVERROR(ENOMEM);
+                goto fail;
+            }
+
+            ost->time_base = encoder_ctx->time_base;
+            ret = avcodec_parameters_from_context(ost->codecpar, encoder_ctx);
+            if (ret < 0) {
+                fprintf(stderr, "Failed to copy the stream parameters. "
+                        "Error code: %s\n", av_err2str(ret));
+                goto fail;
+            }
+
+            /* write the stream header */
+            if ((ret = avformat_write_header(ofmt_ctx, NULL)) < 0) {
+                fprintf(stderr, "Error while writing stream header. "
+                        "Error code: %s\n", av_err2str(ret));
+                goto fail;
+            }
+
+            initialized = 1;
+        }
+
+        if ((ret = encode_write(frame)) < 0)
+            fprintf(stderr, "Error during encoding and writing.\n");
+
+fail:
+        av_frame_free(&frame);
+        if (ret < 0)
+            return ret;
+    }
+    return 0;
+}
+
+int main(int argc, char **argv)
+{
+    int ret = 0;
+    AVPacket dec_pkt;
+    AVCodec *enc_codec;
+
+    if (argc != 4) {
+        fprintf(stderr, "Usage: %s <input file> <encode codec> <output file>\n"
+                "The output format is guessed according to the file extension.\n"
+                "\n", argv[0]);
+        return -1;
+    }
+
+    av_register_all();
+
+    ret = av_hwdevice_ctx_create(&hw_device_ctx, AV_HWDEVICE_TYPE_VAAPI, NULL, NULL, 0);
+    if (ret < 0) {
+        fprintf(stderr, "Failed to create a VAAPI device. Error code: %s\n", av_err2str(ret));
+        return -1;
+    }
+
+    if ((ret = open_input_file(argv[1])) < 0)
+        goto end;
+
+    if (!(enc_codec = avcodec_find_encoder_by_name(argv[2]))) {
+        fprintf(stderr, "Could not find encoder '%s'\n", argv[2]);
+        ret = -1;
+        goto end;
+    }
+
+    if ((ret = (avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, argv[3]))) < 0) {
+        fprintf(stderr, "Failed to deduce output format from file extension. Error code: "
+                "%s\n", av_err2str(ret));
+        goto end;
+    }
+
+    if (!(encoder_ctx = avcodec_alloc_context3(enc_codec))) {
+        ret = AVERROR(ENOMEM);
+        goto end;
+    }
+
+    ret = avio_open(&ofmt_ctx->pb, argv[3], AVIO_FLAG_WRITE);
+    if (ret < 0) {
+        fprintf(stderr, "Cannot open output file. "
+                "Error code: %s\n", av_err2str(ret));
+        goto end;
+    }
+
+    /* read all packets and only transcoding video */
+    while (ret >= 0) {
+        if ((ret = av_read_frame(ifmt_ctx, &dec_pkt)) < 0)
+            break;
+
+        if (video_stream == dec_pkt.stream_index)
+            ret = dec_enc(&dec_pkt, enc_codec);
+
+        av_packet_unref(&dec_pkt);
+    }
+
+    /* flush decoder */
+    dec_pkt.data = NULL;
+    dec_pkt.size = 0;
+    ret = dec_enc(&dec_pkt, enc_codec);
+    av_packet_unref(&dec_pkt);
+
+    /* flush encoder */
+    ret = encode_write(NULL);
+
+    /* write the trailer for output stream */
+    av_write_trailer(ofmt_ctx);
+
+end:
+    avformat_close_input(&ifmt_ctx);
+    avformat_close_input(&ofmt_ctx);
+    avcodec_free_context(&decoder_ctx);
+    avcodec_free_context(&encoder_ctx);
+    av_buffer_unref(&hw_device_ctx);
+    return ret;
+}