[FFmpeg-devel] [PATCH v5] avcodec/libx264: fix extradata when config annexb=0

[Andreas Rheinhardt]

Zhao Zhili:
> From: Zhao Zhili <zhilizhao at tencent.com>
> 
> ---
> v5: Decode chroma_format_idc directly instead of ff_h264_decode_seq_parameter_set
> v4: Fix missing SEI in set_avcc_extradata
> v3: Remove unnecessary inclusion
> 
>  libavcodec/libx264.c | 162 ++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 138 insertions(+), 24 deletions(-)
> 
> diff --git a/libavcodec/libx264.c b/libavcodec/libx264.c
> index 10d646bd76..64cefb5fb0 100644
> --- a/libavcodec/libx264.c
> +++ b/libavcodec/libx264.c
> @@ -38,6 +38,7 @@
>  #include "packet_internal.h"
>  #include "atsc_a53.h"
>  #include "sei.h"
> +#include "golomb.h"
>  
>  #include <x264.h>
>  #include <float.h>
> @@ -865,6 +866,140 @@ static int convert_pix_fmt(enum AVPixelFormat pix_fmt)
>      return 0;
>  }
>  
> +static int save_sei(AVCodecContext *avctx, x264_nal_t *nal)
> +{
> +    X264Context *x4 = avctx->priv_data;
> +
> +    av_log(avctx, AV_LOG_INFO, "%s\n", nal->p_payload + 25);
> +    x4->sei_size = nal->i_payload;
> +    x4->sei = av_malloc(x4->sei_size);
> +    if (!x4->sei)
> +        return AVERROR(ENOMEM);
> +
> +    memcpy(x4->sei, nal->p_payload, nal->i_payload);
> +
> +    return 0;
> +}
> +
> +static int set_avcc_extradata(AVCodecContext *avctx, x264_nal_t *nal, int nnal)
> +{
> +    X264Context *x4 = avctx->priv_data;
> +    x264_nal_t *sps_nal = NULL;
> +    x264_nal_t *pps_nal = NULL;
> +    uint8_t *p, *sps;
> +    int ret;
> +
> +    /* We know it's in the order of SPS/PPS/SEI, but it's not documented in x264 API.
> +     * The x264 param i_sps_id implies there is a single pair of SPS/PPS.
> +     */
> +    for (int i = 0; i < nnal; i++) {
> +        switch (nal[i].i_type) {
> +        case NAL_SPS:
> +            sps_nal = &nal[i];
> +            break;
> +        case NAL_PPS:
> +            pps_nal = &nal[i];
> +            break;
> +        case NAL_SEI:
> +            ret = save_sei(avctx, &nal[i]);
> +            if (ret < 0)
> +                return ret;
> +            break;
> +        }
> +    }
> +    if (!sps_nal || !pps_nal)
> +        return AVERROR_EXTERNAL;
> +
> +    avctx->extradata_size = sps_nal->i_payload + pps_nal->i_payload + 7;
> +    avctx->extradata = av_mallocz(avctx->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
> +    if (!avctx->extradata)
> +        return AVERROR(ENOMEM);
> +
> +    // Now create AVCDecoderConfigurationRecord
> +    p = avctx->extradata;
> +    // Skip size part
> +    sps = sps_nal->p_payload + 4;
> +    *p++ = 1; // version
> +    *p++ = sps[1]; // AVCProfileIndication
> +    *p++ = sps[2]; // profile_compatibility
> +    *p++ = sps[3]; // AVCLevelIndication
> +    *p++ = 0xFF;
> +    *p++ = 0xE0 | 0x01; // 3 bits reserved (111) + 5 bits number of sps
> +    memcpy(p, sps_nal->p_payload + 2, sps_nal->i_payload - 2);
> +    // Make sps has AV_INPUT_BUFFER_PADDING_SIZE padding, so it can be used
> +    // with GetBitContext
> +    sps = p + 2;
> +    p += sps_nal->i_payload - 2;
> +    *p++ = 1;
> +    memcpy(p, pps_nal->p_payload + 2, pps_nal->i_payload - 2);
> +    p += pps_nal->i_payload - 2;
> +
> +    if (sps[3] != 66 && sps[3] != 77 && sps[3] != 88) {
> +        GetBitContext gbc;
> +        int chroma_format_idc;
> +        int bit_depth_luma_minus8, bit_depth_chroma_minus8;
> +
> +        /* It's not possible to have emulation prevention byte before
> +         * bit_depth_chroma_minus8 due to the range of sps id, chroma_format_idc
> +         * and so on. So we can read directly without need to escape emulation
> +         * prevention byte.

There is a slight problem here: You ignore the possibility of
profile_idc being zero. After all, all values not being used are merely
reserved and can be used at any time (although I doubt that they will
ever use this). Shall we ignore this?
The above check (and presumably the ISOBMFF spec for this) uses an
opt-out check for profile, whereas the H.264 spec actually uses an
opt-in check. I just wanted to mention it, feel free to ignore it.

> +         *
> +         * +4 to skip until sps id.
> +         */
> +        init_get_bits8(&gbc, sps + 4, sps_nal->i_payload - 4 - 4);
> +        // Skip sps id
> +        get_ue_golomb_31(&gbc);
> +        chroma_format_idc = get_ue_golomb_31(&gbc);
> +        if (chroma_format_idc == 3)
> +            skip_bits1(&gbc);
> +        bit_depth_luma_minus8 = get_ue_golomb_31(&gbc);
> +        bit_depth_chroma_minus8 = get_ue_golomb_31(&gbc);
> +
> +        *p++ = 0xFC | chroma_format_idc;
> +        *p++ = 0xF8 | bit_depth_luma_minus8;
> +        *p++ = 0xF8 | bit_depth_chroma_minus8;
> +        *p++ = 0;
> +    }
> +    av_assert0(avctx->extradata + avctx->extradata_size >= p);

Does this have to be an av_assert0?

> +    avctx->extradata_size = p - avctx->extradata;
> +
> +    return 0;
> +}
> +
> +static int set_extradata(AVCodecContext *avctx)
> +{
> +    X264Context *x4 = avctx->priv_data;
> +    x264_nal_t *nal;
> +    uint8_t *p;
> +    int nnal, s;
> +
> +    s = x264_encoder_headers(x4->enc, &nal, &nnal);
> +    if (s < 0)
> +        return AVERROR_EXTERNAL;
> +
> +    if (!x4->params.b_annexb)
> +        return set_avcc_extradata(avctx, nal, nnal);
> +
> +    avctx->extradata = p = av_mallocz(s + AV_INPUT_BUFFER_PADDING_SIZE);
> +    if (!p)
> +        return AVERROR(ENOMEM);
> +
> +    for (int i = 0; i < nnal; i++) {
> +        /* Don't put the SEI in extradata. */
> +        if (nal[i].i_type == NAL_SEI) {
> +            s = save_sei(avctx, &nal[i]);
> +            if (s < 0)
> +                return s;
> +            continue;
> +        }
> +        memcpy(p, nal[i].p_payload, nal[i].i_payload);
> +        p += nal[i].i_payload;
> +    }
> +    avctx->extradata_size = p - avctx->extradata;
> +
> +    return 0;
> +}
> +
>  #define PARSE_X264_OPT(name, var)\
>      if (x4->var && x264_param_parse(&x4->params, name, x4->var) < 0) {\
>          av_log(avctx, AV_LOG_ERROR, "Error parsing option '%s' with value '%s'.\n", name, x4->var);\
> @@ -1233,30 +1368,9 @@ FF_ENABLE_DEPRECATION_WARNINGS
>          return AVERROR_EXTERNAL;
>  
>      if (avctx->flags & AV_CODEC_FLAG_GLOBAL_HEADER) {
> -        x264_nal_t *nal;
> -        uint8_t *p;
> -        int nnal, s, i;
> -
> -        s = x264_encoder_headers(x4->enc, &nal, &nnal);
> -        avctx->extradata = p = av_mallocz(s + AV_INPUT_BUFFER_PADDING_SIZE);
> -        if (!p)
> -            return AVERROR(ENOMEM);
> -
> -        for (i = 0; i < nnal; i++) {
> -            /* Don't put the SEI in extradata. */
> -            if (nal[i].i_type == NAL_SEI) {
> -                av_log(avctx, AV_LOG_INFO, "%s\n", nal[i].p_payload+25);
> -                x4->sei_size = nal[i].i_payload;
> -                x4->sei      = av_malloc(x4->sei_size);
> -                if (!x4->sei)
> -                    return AVERROR(ENOMEM);
> -                memcpy(x4->sei, nal[i].p_payload, nal[i].i_payload);
> -                continue;
> -            }
> -            memcpy(p, nal[i].p_payload, nal[i].i_payload);
> -            p += nal[i].i_payload;
> -        }
> -        avctx->extradata_size = p - avctx->extradata;
> +        ret = set_extradata(avctx);
> +        if (ret < 0)
> +            return ret;
>      }
>  
>      cpb_props = ff_encode_add_cpb_side_data(avctx);

You need a golomb configure dependency for get_ue_golomb_31().

- Andreas