FFmpeg Bitstream Filtering使用简介

关键接口

// Query
const AVBitStreamFilter *av_bsf_next(void **opaque);
const AVBitStreamFilter *av_bsf_get_by_name(const char *name);

// Setup
int av_bsf_alloc(const AVBitStreamFilter *filter, AVBSFContext **ctx);
int av_bsf_init(AVBSFContext *ctx);

// Usage
int av_bsf_send_packet(AVBSFContext *ctx, AVPacket *pkt);
int av_bsf_receive_packet(AVBSFContext *ctx, AVPacket *pkt);

// Cleanup
void av_bsf_free(AVBSFContext **ctx);

查询

枚举方式

void *state = NULL;

const AVBitStreamFilter *bsf;

while ((bsf = av_bsf_next(&state)) {
    av_log(NULL, AV_LOG_INFO, "%s\n", bsf->name);
}

通过名称指定

const AVBitStreamFilter *bsf = av_bsf_get_by_name("hevc_mp4toannexb");

设置

AVBSFContext *ctx;

ret = av_bsf_alloc(bsf, &ctx);
if (ret < 0)
    return ret;

ret = avcodec_parameters_copy(ctx->par_in, in->codecpar);
if (ret < 0)
    goto fail;

ctx->time_base_in = in->time_base;

ret = av_bsf_init(ctx);
if (ret < 0)
    goto fail;

ret = avcodec_parameters_copy(out->codecpar, ctx->par_out);
if (ret < 0)
    goto fail;

out->time_base = ctx->time_base_out;

使用

AVPacket *pkt;

while (got_new_packet(&pkt)) {
    ret = av_bsf_send_packet(ctx, pkt);
    if (ret < 0)
        goto fail;

    while ((ret = av_bsf_receive_packet(ctx, pkt)) == 0) {
        yield_packet(pkt);
    }

    if (ret == AVERROR(EAGAIN)
        continue;
    IF (ret == AVERROR_EOF)
        goto end;
    if (ret < 0)
        goto fail;
}

// Flush
ret = av_bsf_send_packet(ctx, NULL);
if (ret < 0)
    goto fail;

while ((ret = av_bsf_receive_packet(ctx, pkt)) == 0) {
    yield_packet(pkt);
}

if (ret != AVERROR_EOF)
    goto fail;

为了让bsf知道是结束了，最后send一个NULL pkt。

释放

av_bsf_free(&ctx);