frame_thread_encoder.c

/*
 * Copyright (c) 2012 Michael Niedermayer <michaelni@gmx.at>
 *
 * 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
 */

#include <stdatomic.h>

#include "frame_thread_encoder.h"

#include "libavutil/avassert.h"
#include "libavutil/cpu.h"
#include "libavutil/opt.h"
#include "libavutil/thread.h"
#include "avcodec.h"
#include "encode.h"
#include "internal.h"
#include "pthread_internal.h"

#define MAX_THREADS 64
/* There can be as many as MAX_THREADS + 1 outstanding tasks.
 * An additional + 1 is needed so that one can distinguish
 * the case of zero and MAX_THREADS + 1 outstanding tasks modulo
 * the number of buffers. */
#define BUFFER_SIZE (MAX_THREADS + 2)

typedef struct{
    AVFrame  *indata;
    AVPacket *outdata;
    int       return_code;
    int       finished;
    int       got_packet;
} Task;

typedef struct{
    AVCodecContext *parent_avctx;

    pthread_mutex_t task_fifo_mutex; /* Used to guard (next_)task_index */
    pthread_cond_t task_fifo_cond;

    unsigned pthread_init_cnt;
    unsigned max_tasks;
    Task tasks[BUFFER_SIZE];
    pthread_mutex_t finished_task_mutex; /* Guards tasks[i].finished */
    pthread_cond_t finished_task_cond;

    unsigned next_task_index;
    unsigned task_index;
    unsigned finished_task_index;

    pthread_t worker[MAX_THREADS];
    atomic_int exit;
} ThreadContext;

#define OFF(member) offsetof(ThreadContext, member)
DEFINE_OFFSET_ARRAY(ThreadContext, thread_ctx, pthread_init_cnt,
                    (OFF(task_fifo_mutex), OFF(finished_task_mutex)),
                    (OFF(task_fifo_cond),  OFF(finished_task_cond)));
#undef OFF

static void * attribute_align_arg worker(void *v){
    AVCodecContext *avctx = v;
    ThreadContext *c = avctx->internal->frame_thread_encoder;

    while (!atomic_load(&c->exit)) {
        int ret;
        AVPacket *pkt;
        AVFrame *frame;
        Task *task;
        unsigned task_index;

        pthread_mutex_lock(&c->task_fifo_mutex);
        while (c->next_task_index == c->task_index || atomic_load(&c->exit)) {
            if (atomic_load(&c->exit)) {
                pthread_mutex_unlock(&c->task_fifo_mutex);
                goto end;
            }
            pthread_cond_wait(&c->task_fifo_cond, &c->task_fifo_mutex);
        }
        task_index         = c->next_task_index;
        c->next_task_index = (c->next_task_index + 1) % c->max_tasks;
        pthread_mutex_unlock(&c->task_fifo_mutex);
        /* The main thread ensures that any two outstanding tasks have
         * different indices, ergo each worker thread owns its element
         * of c->tasks with the exception of finished, which is shared
         * with the main thread and guarded by finished_task_mutex. */
        task  = &c->tasks[task_index];
        frame = task->indata;
        pkt   = task->outdata;

        ret = ff_encode_encode_cb(avctx, pkt, frame, &task->got_packet);
        pthread_mutex_lock(&c->finished_task_mutex);
        task->return_code = ret;
        task->finished    = 1;
        pthread_cond_signal(&c->finished_task_cond);
        pthread_mutex_unlock(&c->finished_task_mutex);
    }
end:
    avcodec_close(avctx);
    av_freep(&avctx);
    return NULL;
}

av_cold int ff_frame_thread_encoder_init(AVCodecContext *avctx)
{
    int i=0;
    ThreadContext *c;
    AVCodecContext *thread_avctx = NULL;
    int ret;

    if(   !(avctx->thread_type & FF_THREAD_FRAME)
       || !(avctx->codec->capabilities & AV_CODEC_CAP_FRAME_THREADS))
        return 0;

    if(   !avctx->thread_count
       && avctx->codec_id == AV_CODEC_ID_MJPEG
       && !(avctx->flags & AV_CODEC_FLAG_QSCALE)) {
        av_log(avctx, AV_LOG_DEBUG,
               "Forcing thread count to 1 for MJPEG encoding, use -thread_type slice "
               "or a constant quantizer if you want to use multiple cpu cores\n");
        avctx->thread_count = 1;
    }
    if(   avctx->thread_count > 1
       && avctx->codec_id == AV_CODEC_ID_MJPEG
       && !(avctx->flags & AV_CODEC_FLAG_QSCALE))
        av_log(avctx, AV_LOG_WARNING,
               "MJPEG CBR encoding works badly with frame multi-threading, consider "
               "using -threads 1, -thread_type slice or a constant quantizer.\n");

    if (avctx->codec_id == AV_CODEC_ID_HUFFYUV ||
        avctx->codec_id == AV_CODEC_ID_FFVHUFF) {
        int warn = 0;
        int64_t tmp;

        if (avctx->flags & AV_CODEC_FLAG_PASS1)
            warn = 1;
        else if (av_opt_get_int(avctx->priv_data, "context", 0, &tmp) >= 0 &&
                 tmp > 0) {
            warn = av_opt_get_int(avctx->priv_data, "non_deterministic", 0, &tmp) < 0
                   || !tmp;
        }
        // huffyuv does not support these with multiple frame threads currently
        if (warn) {
            av_log(avctx, AV_LOG_WARNING,
               "Forcing thread count to 1 for huffyuv encoding with first pass or context 1\n");
            avctx->thread_count = 1;
        }
    }

    if(!avctx->thread_count) {
        avctx->thread_count = av_cpu_count();
        avctx->thread_count = FFMIN(avctx->thread_count, MAX_THREADS);
    }

    if(avctx->thread_count <= 1)
        return 0;

    if(avctx->thread_count > MAX_THREADS)
        return AVERROR(EINVAL);

    av_assert0(!avctx->internal->frame_thread_encoder);
    c = avctx->internal->frame_thread_encoder = av_mallocz(sizeof(ThreadContext));
    if(!c)
        return AVERROR(ENOMEM);

    c->parent_avctx = avctx;

    ret = ff_pthread_init(c, thread_ctx_offsets);
    if (ret < 0)
        goto fail;
    atomic_init(&c->exit, 0);

    c->max_tasks = avctx->thread_count + 2;
    for (unsigned j = 0; j < c->max_tasks; j++) {
        if (!(c->tasks[j].indata  = av_frame_alloc()) ||
            !(c->tasks[j].outdata = av_packet_alloc())) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
    }

    for(i=0; i<avctx->thread_count ; i++){
        void *tmpv;
        thread_avctx = avcodec_alloc_context3(avctx->codec);
        if (!thread_avctx) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
        tmpv = thread_avctx->priv_data;
        *thread_avctx = *avctx;
        thread_avctx->priv_data = tmpv;
        thread_avctx->internal = NULL;
        thread_avctx->hw_frames_ctx = NULL;
        ret = av_opt_copy(thread_avctx, avctx);
        if (ret < 0)
            goto fail;
        if (avctx->codec->priv_class) {
            ret = av_opt_copy(thread_avctx->priv_data, avctx->priv_data);
            if (ret < 0)
                goto fail;
        }
        thread_avctx->thread_count = 1;
        thread_avctx->active_thread_type &= ~FF_THREAD_FRAME;

        if ((ret = avcodec_open2(thread_avctx, avctx->codec, NULL)) < 0)
            goto fail;
        av_assert0(!thread_avctx->internal->frame_thread_encoder);
        thread_avctx->internal->frame_thread_encoder = c;
        if ((ret = pthread_create(&c->worker[i], NULL, worker, thread_avctx))) {
            ret = AVERROR(ret);
            goto fail;
        }
    }

    avctx->active_thread_type = FF_THREAD_FRAME;

    return 0;
fail:
    avcodec_close(thread_avctx);
    av_freep(&thread_avctx);
    avctx->thread_count = i;
    av_log(avctx, AV_LOG_ERROR, "ff_frame_thread_encoder_init failed\n");
    ff_frame_thread_encoder_free(avctx);
    return ret;
}

av_cold void ff_frame_thread_encoder_free(AVCodecContext *avctx)
{
    ThreadContext *c= avctx->internal->frame_thread_encoder;

    /* In case initializing the mutexes/condition variables failed,
     * they must not be used. In this case the thread_count is zero
     * as no thread has been initialized yet. */
    if (avctx->thread_count > 0) {
        pthread_mutex_lock(&c->task_fifo_mutex);
        atomic_store(&c->exit, 1);
        pthread_cond_broadcast(&c->task_fifo_cond);
        pthread_mutex_unlock(&c->task_fifo_mutex);

        for (int i = 0; i < avctx->thread_count; i++)
            pthread_join(c->worker[i], NULL);
    }

    for (unsigned i = 0; i < c->max_tasks; i++) {
        av_frame_free(&c->tasks[i].indata);
        av_packet_free(&c->tasks[i].outdata);
    }

    ff_pthread_free(c, thread_ctx_offsets);
    av_freep(&avctx->internal->frame_thread_encoder);
}

int ff_thread_video_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
                                 AVFrame *frame, int *got_packet_ptr)
{
    ThreadContext *c = avctx->internal->frame_thread_encoder;
    Task *outtask;

    av_assert1(!*got_packet_ptr);

    if(frame){
        av_frame_move_ref(c->tasks[c->task_index].indata, frame);

        pthread_mutex_lock(&c->task_fifo_mutex);
        c->task_index = (c->task_index + 1) % c->max_tasks;
        pthread_cond_signal(&c->task_fifo_cond);
        pthread_mutex_unlock(&c->task_fifo_mutex);
    }

    outtask = &c->tasks[c->finished_task_index];
    pthread_mutex_lock(&c->finished_task_mutex);
    /* The access to task_index in the following code is ok,
     * because it is only ever changed by the main thread. */
    if (c->task_index == c->finished_task_index ||
        (frame && !outtask->finished &&
         (c->task_index - c->finished_task_index + c->max_tasks) % c->max_tasks <= avctx->thread_count)) {
            pthread_mutex_unlock(&c->finished_task_mutex);
            return 0;
        }
    while (!outtask->finished) {
        pthread_cond_wait(&c->finished_task_cond, &c->finished_task_mutex);
    }
    pthread_mutex_unlock(&c->finished_task_mutex);
    /* We now own outtask completely: No worker thread touches it any more,
     * because there is no outstanding task with this index. */
    outtask->finished = 0;
    av_packet_move_ref(pkt, outtask->outdata);
    *got_packet_ptr = outtask->got_packet;
    c->finished_task_index = (c->finished_task_index + 1) % c->max_tasks;

    return outtask->return_code;
}