[FFmpeg-devel] [PATCH 2/2] avcodec/decode: use a packet list to store packet properties

James Almer jamrial at gmail.com
Tue Aug 18 23:25:49 EEST 2020


On 8/18/2020 5:15 PM, Andreas Rheinhardt wrote:
> James Almer:
>> Keeping only the latest packet fed to the decoder works only for decoders that
>> return a frame immediately after every consumed packet. Decoders that consume
>> several packets before they return a frame will fill said frame with properties
>> taken from the last consumed packet instead of the earliest.
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>> This essentially enables decoders implementing the AVCodec.receive_frame API to
>> not require having to deal with timestamps and such properties internally, and
>> letting ff_decode_frame_props() do all the work instead (See libdav1d, which
>> i'll adapt once this goes in).
>>
>> As an example, this fixes the timestamps for the audio track in
>> bink/binkaudio_rdft.bik from the FATE suite, where the decoder wrongly assumed
>> ff_decode_frame_props() alone would handle them right.
>> The reason the relevant fate test is unaffected is because it just compares the
>> decoded output with a reference pcm file.
>>
>> Haven't looked too much into it, but i assume this change could simplify some
>> AV_CODEC_CAP_DELAY decoders that keep track of timestamps, even those using the
>> old AVCodec.decode() API.
>>
>>  libavcodec/decode.c   | 34 +++++++++++++++++++++++++---------
>>  libavcodec/internal.h |  2 ++
>>  libavcodec/utils.c    |  3 +++
>>  3 files changed, 30 insertions(+), 9 deletions(-)
>>
>> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
>> index da587ac1f6..de36e28d3c 100644
>> --- a/libavcodec/decode.c
>> +++ b/libavcodec/decode.c
>> @@ -43,6 +43,7 @@
>>  #include "decode.h"
>>  #include "hwconfig.h"
>>  #include "internal.h"
>> +#include "packet_internal.h"
>>  #include "thread.h"
>>  
>>  typedef struct FramePool {
>> @@ -142,15 +143,22 @@ fail2:
>>      return 0;
>>  }
>>  
>> -static int extract_packet_props(AVCodecInternal *avci, const AVPacket *pkt)
>> +#define IS_EMPTY(pkt) (!(pkt)->data && !(pkt)->side_data_elems)
>> +
>> +static int extract_packet_props(AVCodecInternal *avci, AVPacket *pkt)
>>  {
>>      int ret = 0;
>>  
>> -    av_packet_unref(avci->last_pkt_props);
>> -    if (pkt) {
>> -        ret = av_packet_copy_props(avci->last_pkt_props, pkt);
>> -        if (!ret)
>> -            avci->last_pkt_props->size = pkt->size; // HACK: Needed for ff_decode_frame_props().
>> +    ret = avpriv_packet_list_put(&avci->pkt_props, &avci->pkt_props_tail, pkt,
>> +                                 FF_PACKETLIST_FLAG_REF_PACKET);
>> +    if (ret < 0)
>> +        return ret;
>> +
>> +    if (IS_EMPTY(avci->last_pkt_props)) {
>> +        ret = avpriv_packet_list_get(&avci->pkt_props,
>> +                                     &avci->pkt_props_tail,
>> +                                     avci->last_pkt_props);
>> +        av_assert0(ret != AVERROR(EAGAIN));
>>      }
>>      return ret;
>>  }
>> @@ -512,6 +520,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
>>  
>>      if (ret >= pkt->size || ret < 0) {
>>          av_packet_unref(pkt);
>> +        av_packet_unref(avci->last_pkt_props);
>>      } else {
>>          int consumed = ret;
>>  
>> @@ -550,9 +559,11 @@ static int decode_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
>>  
>>      av_assert0(!frame->buf[0]);
>>  
>> -    if (avctx->codec->receive_frame)
>> +    if (avctx->codec->receive_frame) {
>>          ret = avctx->codec->receive_frame(avctx, frame);
>> -    else
>> +        if (ret != AVERROR(EAGAIN))
>> +            av_packet_unref(avci->last_pkt_props);
>> +    } else
>>          ret = decode_simple_receive_frame(avctx, frame);
>>  
>>      if (ret == AVERROR_EOF)
>> @@ -1683,7 +1694,7 @@ static int add_metadata_from_side_data(const AVPacket *avpkt, AVFrame *frame)
>>  
>>  int ff_decode_frame_props(AVCodecContext *avctx, AVFrame *frame)
>>  {
>> -    const AVPacket *pkt = avctx->internal->last_pkt_props;
>> +    AVPacket *pkt = avctx->internal->last_pkt_props;
>>      int i;
>>      static const struct {
>>          enum AVPacketSideDataType packet;
>> @@ -1701,6 +1712,11 @@ int ff_decode_frame_props(AVCodecContext *avctx, AVFrame *frame)
>>          { AV_PKT_DATA_S12M_TIMECODE,              AV_FRAME_DATA_S12M_TIMECODE },
>>      };
>>  
>> +    if (IS_EMPTY(pkt))
>> +        avpriv_packet_list_get(&avctx->internal->pkt_props,
>> +                               &avctx->internal->pkt_props_tail,
>> +                               pkt);
>> +
> 
> The check below indicates that pkt might be NULL, yet IS_EMPTY(pkt)
> already dereferences it.

That check is bogus even in the current state, anyway. pkt is always
true because avctx->internal->last_pkt_props is allocated and freed with
the AVCodecContext.

> 
>>      if (pkt) {
>>          frame->pts = pkt->pts;
>>  #if FF_API_PKT_PTS
>> diff --git a/libavcodec/internal.h b/libavcodec/internal.h
>> index 5d0e6e7831..ce4dbbc2b9 100644
>> --- a/libavcodec/internal.h
>> +++ b/libavcodec/internal.h
>> @@ -145,6 +145,8 @@ typedef struct AVCodecInternal {
>>       * for decoding.
>>       */
>>      AVPacket *last_pkt_props;
>> +    AVPacketList *pkt_props;
>> +    AVPacketList *pkt_props_tail;
>>  
>>      /**
>>       * temporary buffer used for encoders to store their bitstream
>> diff --git a/libavcodec/utils.c b/libavcodec/utils.c
>> index 14cb5cf1aa..4a180a1500 100644
>> --- a/libavcodec/utils.c
>> +++ b/libavcodec/utils.c
>> @@ -50,6 +50,7 @@
>>  #include "thread.h"
>>  #include "frame_thread_encoder.h"
>>  #include "internal.h"
>> +#include "packet_internal.h"
>>  #include "put_bits.h"
>>  #include "raw.h"
>>  #include "bytestream.h"
>> @@ -1149,6 +1150,8 @@ av_cold int avcodec_close(AVCodecContext *avctx)
>>          av_packet_free(&avctx->internal->compat_encode_packet);
>>          av_packet_free(&avctx->internal->buffer_pkt);
>>          av_packet_free(&avctx->internal->last_pkt_props);
>> +        avpriv_packet_list_free(&avctx->internal->pkt_props,
>> +                                &avctx->internal->pkt_props_tail);
>>  
>>          av_packet_free(&avctx->internal->ds.in_pkt);
>>          av_frame_free(&avctx->internal->es.in_frame);
>>
> 
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> 
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
> 



More information about the ffmpeg-devel mailing list